> Raspberry Pi OS is only based on Debian bookworm (released in 2023) and very explicitly does not support a key Debian feature: you can’t upgrade from one Raspberry Pi OS release to the next, so it’s a complete reinstall every 2 years instead of just an upgrade.

What? I've upgraded my RPis in-place every single time there's a new OS release. They don't support upgrading that way, perhaps, but I've never had a problem.

And even for official Debian releases, they recommend you do a full backup, because it might not work.