I think that installation was originally 18.04 and I installed it when it was released. A while ago anyways and I've been upgrading it as new versions roll out and with the latest upgrade and snapd software it has become more and more annoying to keep the operating system happy and out of my way so I can do whatever I need to do on the computer.
Snap updates have been annoying and they randomly (and temporarily) broke stuff while some update process was running on background, but as whole reinstallation is a pain in the rear I have just swallowed the annoyance and kept the thing running.
But now today, when I planned that I'd spend the day with paperwork and other "administrative" things I've been pushing off due to life being busy, I booted the computer and primary monitor was dead, secondary has resolution of something like 1024x768, nvidia drivers are absent and usability in general just isn't there.
After couple of swear words I thought that ok, I'll fix this, I'll install all the updates and make the system happy again. But no. That's not going to happen, at least not very easily.
I'm running LUKS encryption and thus I have a separate boot -partition. 700MB of it. I don't remember if installer recommended that or if I just threw some reasonable sounding amount on the installer. No matter where that originally came from, it should be enough (this other ubuntu I'm writing this with has 157MB stored on /boot). I removed older kernels, but still the installer claims that I need at least 480MB (or something like that) free space on /boot, but the single kernel image, initrd and whatever crap it includes consumes 280MB (or so). So apt just fails on upgrade as it can't generate new initrd or whatever it tries to do.
So I grabbed my ventoy-drive, downloaded latest mint ISO on it and instead of doing something productive I planned to do I'll spend couple of hours at reinstalling the whole system. It'll be quite a while before I install ubuntu on anything.
And it's not just this one broken update, like I mentioned I've had a lot of issues with the setup and at least majority of them is caused by ubuntu and it's package management. This was just a tipping point to finally leave that abusive relationship with my tool and set it up so that I can actually use it instead of figuring out what's broken now and next.
I’ve upgraded several Ubuntu LTS versions to newer LTS and have been running fine. The problems come up when you wait too long and the repos don’t have the needed packages anymore. You can still fuddle your way through even that scenario and retain a fully working system.
I’m glad we have companies helping to push the envelope and try new things. I may not always like the direction they take things, e.g., the Unity desktop turned me off for a few releases, and I always seem to run KDE since gnome went off the rails (imo), but it doesn’t hurt anything and the whole ecosystem is probably better for it. If it hurts then people move to alternatives and hopefully Canonical backpedals, or people move on and Ubuntu withers.
Or at least you used to have that option without too much of a headache. I'm pretty sure you can still do it tho, but the steps required to 'rescue' old installation tend to be more complex than they used to be.
For a desktop system, I think something like NixOS is probably the way to go. Keep your home partition then blow away the system and boot if there are ever any issues then install the system from your backed-up system config file and you’re golden.