Dell Latitude 5310. Cheap on ebay, 10th-gen Intel i5, often comes with 16GB RAM and has the capability to go to 32GB RAM, can upgrade the ssd, wifi, and RAM, and it has a 60Whr battery. It will literally go all day on battery. You may have to replace the battery due to age, but otherwise for a 13.3" laptop it is very good and still performs. It also supports Windows 11, but I suppose you will Linux it. It’ll do it either way.