Linux

I encrypt everything, with unique complex passwords, that I have a safe mnemonic system for remembering and retrieving.

Yeah all my drives are encrypted with LUKS mostly because of home burglaries (bad area and whatnot). I still keep backups regardless on drives that are also encrypted

Absolutely. LUKS full disk encryption. Comes as an opt-in checkbox on Ubuntu, for example.

And I too cannot understand why this is not opt-out rather than opt-in. Apparently we've decided that only normies on corporate spyware OSs need security, and we don't.

No need as none of them are networked

Depends. On external drives yes. On internal boot drive no. I had performance issues and thermal issues with it so stopped on boot drives.

I always encrypt my computer SSD as well as my external backup drive. I just wish that when installing a Linux distro and when selecting encryption that it would work with multiple drives

Only encrypt the home partition, for the root partition it just unnecessarily slows down the system.

Also, I think, there could be different approaches instead of encryption. AFAIK, android doesn't use encryption underneath, but uses a semi-closed bootloader (which means, if you install a different OS, all user data gets wiped). I'm currently investigating the feasibility of such an approach in the long term.