Rogue
How regularly do you really need them? Surely by the time you come to reinstall an OS there’s already a later version available, doesn’t it just make sense to create a fresh USB each time?
For example about a month ago I installed Project Bluefin on a couple of devices so that USB is lying around somewhere. But in the meantime the maintainers have rotated the update signing keys so that month old installer is now redundant.
Isn’t it just far easier to transfer documents using one of the thousands of cloud apps though? Since Dropbox and such became a thing I’ve not had a use for USBs. If it’s privacy that concerns you then you already mentioned self hosted services and I’m sure there’s a few Dropbox clones among them.
There’s not much point in survival PDFs unless you’re also carrying a laptop to view them on.
If you really do want to go full apocalypse prepper then track down an archive of Wikipedia and various how-to websites.
The reason you’re struggling to think of anything to put on it is because you don’t need to be carrying a USB drive.
No aircraft cabin crew have ever put out a call asking if there are any Linux sysadmin onboard with a copy of GParted Live v1.5.0 for 32bit ARM devices .
What are your issues with Fedora? I’d really recommend giving one or more of the universal blue OSs ago regardless as they’re pretty far from native Silverblue. Project Bluefin for instance has a solidly Ubuntu feel.
edit: reading your responses elsewhere I can guarantee you won’t have the same update/reliability issues you had with Fedora because the universal blue model is entirely different