I don't daily drive my old computers.
The bulk of what I do is related to engineering (mostly software), audio (consumption and creation) and games. I've tried to find a productive purpose for any of my old boxes and I keep failing.
I have a really nice 1040STe config, with VGA output, SD card HDD, PS/2 mouse, maxed RAM. It was my intent for years, to utilize this computer for music. But even if I had a chiptune-alike idea, it would be way faster to realize it on a modern DAW, trading off that 1% of original hardware sound fidelity for a 50 times better interface and capabilities. From the get go, there is so many cables and connections around the Atari just to use MIDI. The upscaler needs power, the SD card interface needs power, the MIDI keyboard needs power. It's a whole bunch of stuff needed for something rather simple on modern platform.
If I had a space/garage for these setups it would be ok, but in a modest living space, there is no room to keep old boxes around, every device permanently installed needs carefully thought out placement and cable management. Not to mention old boxes and modern living space are apples and oranges when it comes to interior design.
I just went through a good example of the circle that I find myself in every time I think I got a purpose - lately felt like playing Heroes 2, and the complete version with CD audio stutters on dosbox. As I have a permanently installed Windows 95 machine, and there is Windows version (WinG) of the game, I said to myself well ain't that nice, now I have an use case for the Pentium box. The game runs ok, but still isn't completely fluid. Meanwhile I found out there is an engine rewrite called fheroes2 which works perfectly on modern platforms.
Even if og game worked as fluid as this modern version, I would still restorage the Pentium box in a day or two. Because it's just not convenient. It would have CRT connected to it because there is no way I'd go for permanent retro setup with LCD, it's just not correct.
The effective volume of slim desktop Olivetti case and Syncmaster 17" atop of it rivals the rack that houses the entirety of my modern platform, computer, networking and audio devices + power routing. It's just not practical.
So yeah, finding it hard to use retro platforms even for retro purposes let alone daily drive on them.
I would love to hear more about others running modern OSes like Linux or BSDs and actually using their machines. Older OSes are cool to as your still getting use out of the machine of course.
I've done some tinkering with FreeBSD 5.4 (year 2005) on a MMX system using TNT2 or GeForce2 AGP. The idle usage of system with full GUI (XFree86+Windowmaker) was 20MB.
For desktop it is pretty unusable below 128MB RAM because Unix applications, especially X11 ones are not memory friendly like DOS stuff.
The FreeBSD package archive still works so you can just install whatever was used then, Opera Browser, early Firefoxes, etc. Quake 2, works normally, meh on TNT2 and superb on Geforce ofc.
I'm sure this is also possible on Linux systems such as Debian. It should also be possible to compile newer versions of software than in package archive that was frozen in 2005.
Linux/BSDs are a good use case, because the software has changed. There's a myriad of early toolkit applications that look pretty shitty on modern desktops or don't work at all.