I have had USB thumb drives that just wouldn’t boot on some computers. Try a different USB drive maybe.

https://lwn.net/Articles/335415/

The evince PDF reader ran into this issue back in 2005. It is now rare to find a distributor shipping a version of evince which implements copy restrictions. Xpdf implements copy restrictions unconditionally, but Debian patched that code out in 2002, and that patch has spread to other distributors as well. In general, as one would expect, free PDF readers tend not to implement this behavior. Okular is about the only exception that your editor can find; it’s interesting to note that the version of Okular shipped with Fedora Rawhide also implements copy restrictions by default. Perhaps this behavior is result of the relative newness of this application; as it accumulates more users, the pressure for more user-friendly behavior is likely to grow.

Another downside of flatpak is that I don’t trust upstream devs to have my best interests at heart, but I trust Debian developers far more. I’ve seen upstream do some annoying or stupid shit and the Debian maintainers not budging.

I think it was poppler or evince that decided they were going to enforce the no-copy-and-paste bit you can set on pdfs. Debian patched it out. I’ve seen Mozilla decide they were going to enforce their trademarks. They carved out special exceptions for various distros but that still would have meant you would have to rename Firefox if you were to fork Debian. Debian had none of it. There were many dodgy copyright and licensing problems upstream devs gave no shit about. Debian not including these often eventually put pressure on them to fix this shit or for some replacement to get developed.