RIP to your thinkpad during stats, brutal timing ngl. since you are used to building desktops, you probably appreciate a machine that just works without a ton of bloatware. i would suggest tracking down the Lenovo IdeaPad Slim 5 16 inch Ryzen 7 16GB RAM if you can find it on sale right now, usually sits right around your budget and the keyboard is honestly top tier for those late night typing sessions. battery life is solid enough for a full day lugging it around boston too. another one to watch is the Acer Swift Go 14 OLED 16GB RAM which goes on deep discounts pretty often. just be careful with some of the cheaper models out there that lock you into 8gb ram since you cant upgrade it later. let me know if you need help hunting down a current coupon code for either of those.

Building on the earlier suggestion, you gotta check out the ASUS Zenbook 14 OLED 14 inch Ryzen 5 16GB RAM. I grabbed one on sale last month for my master's classes and the battery easily lasts me all day walking across campus. The screen is gorgeous and honestly the keyboard feels super snappy for late night typing sessions. Plus it stays well under your eight hundred dollar limit so you can save some cash for textbooks!