Those 15-20 years, it was the same Debian install. Everything else in the computer changed, but Debian kept on ticking.
There was a while Debian was behind on supporting things like laptop power management and graphics cards, when I switched to Ubuntu. For a while, it was a more polished, user-friendly up-to-date Debian. That was nice.
Now that Ubuntu re-invents the wheel each new release (and quite often, replacing a spoked, pneumatic-tired wheel with a square piece of wood), and hardware support is a little more standardized, I think it's time to switch back. It feels more like a tech gizmo, designed for Ubuntu developers, than an end-user OS.
The Debian wiki page on fonts is helpful. The Arch wiki page is better, and most of it still applies:
When was this? I can confirm that it breaks from time to time but usually that means I haven't rebooted for four months and by restarting everything, it all works again. I never needed to dive into the font system at all while using Debian stable or testing in the past 5+ years with Cinnamon as DE. (Firefox, not from the repositories, being the exception where one might need to toggle gfx.canvas.azure.backends in about:config.)