My recommendation for that price range is to buy a used business-class laptop. Emphasis on the business-class. These are the Dell Latitudes and the HP ProBooks. Try to find something less-than five years old (businesses tend to phase out older laptops in the three or four year mark). Buy from a reputable re-seller that offers support in case you get a lemon.
It won’t be the fastest or sexiest laptop out there. But it will be long lasting and reliable.
Just use Debian. Why use the inferior downstream distros when you can go right to the OG? You are already halfway there.
Debian doesn’t have a corporate sponsor so there is no risk of getting spammed or giving someone your personal information.