The good thing is that you can do all this jailbreaking with free software from Linux, apparently. Of course it's endless browsing shadier and shadier / scammy websites before finding something that looks somewhat less shady. The world of iOS jailnreaking is very strange.
The bad thing is that sideloading requires an Apple account. I don't have one. Creating an Apple account from the device is not possible anymore. Creating an apple account from the apple website seems complicated. It wants a phone number which I'm not willing to give. I tried these services that provide burner public phone numbers to get the verification code it wants but have yet to find one that works. When i manage to get a verification code, it tells me that this is not possible at this time, please try from an Apple device. I don't have another one. I suppose I could try to run macOS in a virtual machine just for this.
I'd like to make this device useful. Up to recently I could use it to display music scores in PDF, I even wrote a web app for it to annotate them, but the screen is a bit broken and this makes the touchscreen very erratic to the point of being unusable.
I'd be happy to make it useful for something else but on the other end, I have other things more interesting to do than to deal with Apple's bullshit.
Too bad.