I went through the purchase & install process for AltStore in the EU, and it's not really any more onerous than downloading a Mac app or installing a provisioning profile. One trip to Settings to ‘Allow’, and you can tap through the install dialogs in a second.
The install confirmation sheet, which provides metadata and screenshots about the app and its publisher, is kinda a nice thing to have? Honestly wouldn't surprise me if this system came back to macOS, too (if developers don't revolt)
@stroughtonsmith I screwed up obviously, I clicked back at the first screen. Now I see no way to download store or manage subscription without new payment. 😣