Another interesting point from these times: it was even then often written that the Linux and Ubuntu are better for the use of older computers compared to Windows. That wasn't true either. With every new version less of my hardware worked as expected. The memory demands only for the GUI installer were bigger than the demands of Windows, forcing me to attempt to install from the text mode, and still having the issues later. Windows just worked on the same machine (with the existing drivers).
I've also lived through my (other) old hardware breaking on Windows too: my notebook on which all the hardware worked as expected on Windows 7 was declared by the Windows 10 as "totally would work" and it totally didn't -- the Intel devices on it never got the drivers that worked on Windows 10, neither by Microsoft nor by Intel who simply stopped supporting them.
No OS is immune from the scenario (or even the company claims) "it will work" which than turns out not to be true with a new version.
Long story short, in this case, backup your /home, install from scratch. Backups are good anyway. Any other attempt will probably give more pain. Also don't expect the newest OS to always work with the old hardware. Be prepared for these kinds of events too.
For a real long term, there's Red Hat.