That's odd, I can remember back in my day that Samsung-s were like the first thing they poked with because pretty much everyone used Samsung phones. Maybe they did something to their bootloader or something...?

I won't blame you for not knowing, though, but now that the writing is on the wall, better be sure before buying another phone about compatibility for third party OSes, if not one that comes with one already installed

Yeah you really need to check the Wiki before shopping. OnePlus is a pretty good choice. That's what I had until switching to GrapheneOS (Pixel devices only for now, something from Moto next year).

if you can unlock the phone, you can install a treble GSI build of lineageos