Okay, first, all credit where credit is due. I did not come up with this fix myself. I lost my semi-tethered Jailbreak on my iPhone (Electra) and was unable to get Electra back on there (after a while, even though I have not updated my iOS past 11.0.1 to hold the JB, the Electra app for Jailbreaking fails to open on my iPhone). Then, when I went to use Cydia Impactor to get it back on there, I got a “Provisioning error 81/Please update XCode to version 7.3 or newer”. This, by the way, is on my MacBook; all these instructions are for jailbreaking on a Mac, not a Windows machine, but it might work for Windows, too; I don’t know; see if you can download XCode for Windows, I think you can, because that’s the first step (see below).

So, this method, again, not mine — it’s from autumn-autumn on Reddit — allows you to sideload the Jailbreak IPA (Electra, unc0ver) using XCode. So I’m just going to repost autumn-autumn’s workaround and clean it up a little bit, plus add a few refinements of my own dealing with errors I ran into. Here we go:

1. Install XCode. You need the new disc image file for it (.dmg). I opted for the newest .dmg file available, which was Xcode 7.3. If you want any version of Xcode, here they all are: https://developer.apple.com/download/more/
2. It’s going to take a long time to download. Go watch TV for an hour or something. Next, click on the darn thing and move/install it to the applications folder and open it; this also going to take a long time, but just bear with it, this DOES work. Autumn-autumn got an error message that could only be solved by first opening console to read through the error log, then going into settings, date & time, manually set, change system date to a date before the certificate for Xcode expired, then save, and try again. That should work. *Note: I did not get these errors — Kip
3. Now, open XCode. Go to File -> Preferences and add your Apple ID. Double click on the ID in the right hand box once added, a window will open. Click the CREATE button on the right side of window. (*Note: This did not quite work as described for me. Just add your Apple ID and password under Preferences, then File -> New or New Project, I forget) to create a new single project in Xcode (*Note: You’re going to see a lot of options here. I chose the second one, which was, I think, “Single Display Page App”. It worked. I don’t know if all the other options work or not, as I did not try them all –Kip) Attach your device to the computer with a cord. Select your device in the top left bar. Select your Apple ID as the “team”. (*Note: I did not see “team” but I did see a place in the project to add my developer account. Use an iPhone Developer account, do NOT use “Mac Developer”. The option will be the second or third box down — Kip) Leave all other defaults as is. Set this aside, we are coming back in a moment.
4. Go get the latest support files for your iOS. Xcode may not have them. Mine did not, I was using an older version. Here they are: https://github.com/filsv/iPhoneOSDeviceSupport . I downloaded the zip, then expanded and saved in Applications, right-click, “Open Applications”, Right-click Xcode > Show Package Contents, go to Developer > Platforms > iPhoneOS.platform > DeviceSupport. Save here and close out. Quit Xcode. (*Note — This part is crucial; I did have the same problem; I’m still running 11.0.1, so I downloaded the “11” folder from the link above, put it in the path mentioned, and it fixed all problems –Kip).
5. Launch Xcode again. Make sure your device is attached. Watch the little status bar thing do its little status bar dance, top of page. When it says ready or something like that, you should be able to click the arrow looking button (play) in the top bar, or manually click run. See what fun error message you get (*Note: This is almost always due to not having the iOS support files, see above, Step 4, to get the right ones, again –Kip), or maybe it’ll be well behaved and actually RUN. If so, you must now go into settings –> general –> device management (on your phone) and TRUST yourself as a developer (*Note: This can be a little tricky to do or you may not even actually have to do it; somehow my iPhone automatically trusted me. Also, at some point early in this process, you may get a yellow warning icon in Xcode that says your Provisioning is having problems — use the “Fix” button underneath it to keep fixing until there are no more problems. Also, when you run the actual code, you may get some warning messages on the left; pay them no mind unless the operation cannot successfully run; I ran it and got warning messages but it executed on my iPhone as it should have, no problems– Kip)
6. When it successfully runs the project on the target device and you’ve “trusted” yourself as the app developer, download iOS App Signer: https://dantheman827.github.io/ios-app-signer/ and follow the instructions.
7. This is where that useless “project” you created and ran in the steps above comes in. You’re going to use that thing as a vessel for whatever it is you want to sign & sideload (*Note: Brilliant, autumn-autumn; this method is actually really pretty darned easy after you install Xcode). Now you need to add the .IPA for whatever jailbreak app you’re using, and you’re going to need the code signed. Open iOS App Signer –> INPUT FILE is that jailbreak app you want to sideload (this was unc0ver for me (*Note: I use Electra, and it worked fine for me, as well), SIGNING CERTIFICATE should have some sort of reference to your Apple ID in there, PROVISIONING PROFILE — for that select that “project” you created. Click start. It will want you to choose an output path and name of file. (*IMPORTANT NOTE* — Be sure to sign the code with your iPhone Developer certificate, not your Mac Developer one. Also, when I finally figured out I had to use iPhone Developer, it gave me a message that there were problems signing my code; self fix did not fix them; if you get that message, go into your Keychain and delete all the certificates that say iPhone Developer — JUST those certificates — and then run Xcode again, just start it up, it should generate new certificates for you; I was stuck on this part for a while, shoot me a comment if you’re having problems here –Kip).
8. This will create a ready-to-use file. Go back to Xcode once completed, click on devices (Window -> Devices); select your device. At the bottom, it will show loaded apps. Drag and drop the .IPA of the app you want to sideload (Note: In my case, Electra; many people are using unc0ver these days. though –Kip) or hit the plus sign, and that will sideload the NEWLY SIGNED app. This should do it. It should now be on your device and ready for use.

Again, ALL CREDIT GOES TO autumn-autumn on Reddit for finding this workaround. As far as I know, it is currently the only way to sideload an IPA; all the impactor apps, including the original Cydia Impactor, no longer work. And, note, it DOES WORK. It took me a night and an afternoon to get it right, but now my iPhone is jailbroken again. Believe it or not, the method listed above is the easiest (and perhaps, currently, only) way to sideload apps. It’ll sideload other .IPAs, too, I would imagine, if you actually want to code a new app or something, LOL, but you’re probably just going to be using it to sideload the Electra IPA or the unc0ver IPA.

Also, once you do it one time, you’ll learn pretty fast that, now that you know what to do, it’s not actually that hard; it’s just a bit of a learning curve with Xcode, if you’ve never used it before, plus, downloading and installing Xcode are by far the longest things you’re going to be doing. REMEMBER: You want to make sure you have the support files for the right iOS you have, and you want to make sure you put “iPhone Developer” into that, I believe, second box in iOS Signer, NOT Mac Developer, and iPhone Developer may give you some problems; again, you need to delete all the iPhone Developer certificates from your keychain and re-launch Xcode to get new certificates that work.

One last thing — at some point you are, I think, required to enter what’s called an “app specific password” from Apple. Here’s a link with an easy step-by-step guide for creating an app specific password from Apple. It’s really easy, much easier than you might think. and if you’ve ever used Cydia Impactor to jailbreak, you know how to do it already. But, anyway, here’s the link to it: https://www.imore.com/how-generate-app-specific-passwords-iphone-ipad-mac .

If you have any issues with this, reply below, and I’ll do my best to answer your questions. All I can say for now is: this method works with an iPhone 8 Plus running iOS 11.0.1. I imagine eventually saurik & company will fix Cydia Impactor but I wouldn’t hold your breath. In the meantime, this workaround, though it takes a while (mostly to download, copy, and open Xcode the first time) and again I have only tried using the above method using a MacBook as it was written intended for use on a Mac. If you have a Windows PC (which I do), you can try the same above steps — if you do, please let me know if this works on Windows as well. All I can say is, I’m glad I have a MacBook as a backup, even if it’s years out of date and the battery is shot. Don’t care; it’s still a lovely little machine that does its job very well, and I usually use it to jailbreak all the time, over my PC, because the PC jailbreaks of late have been rather iffy with me.

Good luck, and again, if you have problems or questions, please submit a comment and I will do my best to help you. Happy jailbreaking!