I would not buy a Pentium, an i5 seems OK but in 2021 you’re probably going to do better price/performance-wise by looking at Rysen systems. The saving grace of the first system you linked to was USB-C charging, which typically I say is a hard requirement. I guess if your extremely budget-conscious then maybe you look past it, but personally, I’d rather dig through used laptops and try to find something last generation with decent specs and perhaps thunderbolt if you really plan on using the thing full-time. I would also make sure any laptop I bought had one or two M.2 slots (supporting NVMe), upgradable RAM, and personally I’d gauk at anything with an optical drive.

But the best advice for buying a linux laptop is searching forums and the arch wiki for guides and threads about people setting it up. Make sure the bluetooth and wifi are compatible (or at least easily swappable), that the system can enter deep sleep states (S3/S5), that it has support for Virtualization (the i5 should), and that the thermals are good enough that it doesn’t sound like a jet engine in Linux.