I recently wimped out of buying a thinkpad due to uncertainty regarding getting Ubuntu running correctly and the time it would take me to do it. Do you have a guide you’ve used or instructions you have stashed somewhere?
There are two reasons for this - Fedora ships a far more recent kernel than most distros (the only competitor being Arch), and Redhat does a lot of work on Thinkpad support. On my T430 at home literally everything worked out of the box with zero config, all the way down to fingerprint reader and keyboard backlight.
I would recommend PopOS over plain Ubuntu because they have some nice utilities for managing things like hidpi, and in my experience hardware "just works" more often, e.g. wifi.
Caveat, I didn't get the discrete GPU, those can be hell, and I made sure to get an Intel wifi chipset (same price) since it has the best Linux support.
Things get a bit fiddly if you want to use something like Manjaro or Fedora. But even then, it all just works.
There were some BIOS settings to change first to get the machine dual-boot ready, nothing fancy so as I don't even remember what it was. Getting a bootable USB stick was more challenging for me!