Thinkpads were basically made for Linux, depending on your Budget you can get a Thinkpad X220, X230, T420 or T430 for small money - perfectly usesble machines and Linux (my experience is CachyOS & Arch) work out of the box.
For a bigger budget i could recomment the T480, it’s still upgradeable.
And for a bigger budget i’d recommend a T14 GEN2



unfortunately not, power wise it only lets you upgrade the RAM.
but those CPU´s are vastly superior to those 2nd and 3rd Gen i7´s you can put into a t420/t430
the german website https://thinkwiki.de/ has detailed information about possible upgrades of every model :)