I also agree with this sentiment. I got a used t440p which I used for years in school before upgrading to the framework 13. I still love my old thinkpad, but its now my cheap in home media server. I would agree that old thinkpad are easy to find and a cheap (but still very useable and still to some extent repairable) option for work and school.
I’m going to add my +1 for framework, I got the batch 5 original framework 13 with pop os on it and a windows 10 copy on a 250gb expansion card. Its been my main work and play laptop and I enen replaced the main chassis after it got smashed (long story) involving the sidewalk. Anyway I love what framework is doing and the decision has arguably already paid off within these last two years.