Hey Fred11,
you are right, there are many Linux distributions that run on older hardware. At the moment I recommend using the desktop-live image of Devuan, it uses the graphical Refracta installer which is much more pleasant and easier than the standard installer. I was surprised how pleasant it is, and installation goes very fast with it.
However, installing a Linux-based operating system usually comes with more learning than with other operating systems. But there is a large support community.
Yes I know, today’s laptops and tablets are so thin that the Ethernet port doesn’t fit anymore. But that’s no problem, for very little money you can get a USB-to-Ethernet Adapter. I use them a lot.