Lenovo ThinkPads work very nicely with Linux, and there's a large second-hand market. The T and X series are especially great I find.
The usual advice about avoiding soldered RAM holds in general, but right now used laptops are being bought just for stripping RAM. So I think putting up with soldered RAM in second hand devices (I'd go for at least 32G) can be a smart move because it may be a better deal (and often a smaller form factor).
This is not difficult to achieve at all with tools like sed or awk. But unless you provide a concrete example input file or files, all we can do is point to those tools.
Interesting question, here are some EU-made indie games I've enjoyed, in no particular order. I've had to look all of these up, I didn't play them because they were European or anything.
Start with ctrl+p, ctrl+a but yes