my brother runs a thinkpad T380. best thing about it is that there is a swappable and a built-in battery. he bought it “refurbished” so his didn’t include the internal one for some reason. but you can open and even upgrade some components.
all for around 300€.
we think these have benn bought by companies for full price (1000+€) and are now being replaced, so the market for used thinkpads is very saturated at the moment.
currently runs windows, but i see no problems with running linux on a laptop, you aren’t gonna game on integrated graphics anyway.
i’ve used Linux Mint Cinnamon a fair bit, i really like it. i’ve heard KDE offers more desktop customization, but i have no idea what that would actually look like. Kubuntu apparently has it.