Out of the options you mentioned, Pixel with a custom rom (GrapheneOS, CalyxOS, etc.) is probably the best bet. Seconded by any Samsung that could run a custom rom, though I agree with others here that the hardware is better on the Pixels. Plus they have extra security hardware features that will be better. Of course, if things are weird with your telecom, that might effect things (trust me, been there with an Ubuntu Touch phone before.)
Another option you could look at depending on where you are is Murena's phones. They have a bunch of options pre-flashed with their de-Googled rom /e/ os. Not my favorite rom, but still not bad! And of course those can be flashed with another rom if you want as well!
That's why I never got why TPUSA people go around "debating" people on college campuses. They never actually want a debate, they just want to tell you you're wrong.
You might be able to find a super lightweight desktop distro out there (I think Damn Small Linux can run on those specs?) or you could repurpose it as a basic server of some sort like you mentioned. Unless you wanted to invest in some cheap old ram to throw in there and maybe make it a bit faster, then I think those would be your best options.
I've been using it on my Fedora laptop for the past week or so and it's really nice, even in alpha 1! Can't wait to see how it turns out fully finished!
Generally I have when I use Gnome or KDE on Linux, though I have started to prefer MATE, which doesn't have Wayland support yet afaik. I also started using FreeBSD on one of my computers a bit more, and I believe Wayland support is still a bit wonky on that right now. But as soon as Wayland support is there I'm definitely switching to that on the daily.
Out of the options you mentioned, Pixel with a custom rom (GrapheneOS, CalyxOS, etc.) is probably the best bet. Seconded by any Samsung that could run a custom rom, though I agree with others here that the hardware is better on the Pixels. Plus they have extra security hardware features that will be better. Of course, if things are weird with your telecom, that might effect things (trust me, been there with an Ubuntu Touch phone before.)
Another option you could look at depending on where you are is Murena's phones. They have a bunch of options pre-flashed with their de-Googled rom /e/ os. Not my favorite rom, but still not bad! And of course those can be flashed with another rom if you want as well!