Depending on the laptop (or with any laptop + smart plug) you can set charging thresholds, both for starting and stopping the charge (lower and upper limits), this way it will do a few cycles instead of staying fixed to a certain level of charge.

In order the worst things we can do to batteries are: leave them at 0% for years, leave them at 100% for years, leave them halfway for years (what happens when left plugged in with only an upper charge limit like 80%) - batteries need to do a few partial cycles at least, once in a while.

I recently added a used mini pc to my lab and it has a Ryzen 3550H, 16GB ram and 512GB nvme; it cost less than 100€ total, hits almost 8000 passmark. Just to give you an idea of what you can get on the used market, I wouldn’t buy a new Celeron pc myself.