I work on Linux and use Linux at home. I'll try to go through the problems you mentioned:

1. Just run the update command again in the GUI or terminal. If it doesn't work, we'll have to dig into apt with verbose logs but I haven't had apt break on me for over a decade unless I deleted something I shouldn't have.
2. Is Firefox installed as a snap/flatpak? That only happens with me occasionally when I installed flatpaks, they're just slower. Canonical can be a real arse about this stuff, they might switch packages to snaps without telling you and you might only come to know about it once you dig deeper.
3. All of these issues seem to related to your storage medium. Is the SSD OK? Open up the process monitor, sort by ascending order of disk writes/reads and open your applications one by one to see which one of them is the culprit.
4. Rebooting suddenly is not normal. Unfortunately, you'll have to go through logs for this one. Simple ones are dmesg and journalctl, we can dig deeper into them if you want to.

If I had my hands on your laptop I'd be running a vulnerability scan by now but I don't think the problem is serious enough to warrant it.

Linux has always been the way you've described across many different distros for me over the years.

By far the most stable for me was Fedora. I've been running CachyOS over the last year or so and it's been solid.

Until today. For some reason KDE takes forever to startup now. A few apps have this problem as well.

Like @wildbus8979@sh.itjust.works just said, run memory test.

What hw do you have in that laptop?

something went wrong, but we're not sure what it is.

Check the system journal with

sudo journalctl -e

Do your issues appear on a fresh install? At my admittedly limited level of expertise, I'd probably start from there. If a clean install works properly, then something that's happening later is messing it up. You'd have to keep track of changes you make to your system and check for issues as you go.

If a clean install is borked from the get-go, maybe try different distros. Since Framework supports Fedora, I'm surprised that anything would go wrong.

I don't know if Framework offers any support or warranty, but you could check with them too.

I use Zorin OS 17 (based on ubuntu) on a desktop AMD based system and a framework laptop 16 for about a year now and even before that used an older version of Zorin OS for about 4 years on a shitty lenovo laptop and never had any stability problems. Even the lenovo still runs reliably.

The only problem I've had on the desktop is that the linux driver for an ntfs formatted drive constantly corrupted my data on that drive to the point where some of the data got lost. All other drives are formatted with ext4 and work without any problems. Maybe your problems could be similar?

If you want to try a distro that can just work for you, instead of reading about it, do this:

• Aurora if you don't do gaming.
• Bazzite if you play games.

They are both from the Universal Blue family of distros which are based on Fedora Silverblue.

They are all immutable and atomic. They won't break. They will be more stable than windows. It will be easy. And it will come with batteries included.

Also, if you do gaming and are also a developer, there's bazzite-dx which will be releasing soon.

If you're on the 24.04 LTS release it might be worth upgrading to 24.10, as it has a lot of bug fixes and improvements from upstream, especially if you have a recent Framework board. Although it isn't your preferred option to change distros, it may be worth giving openSUSE Tumbleweed at least a test drive to see if it's an issue with your laptop or just an Ubuntu issue, as I have had Ubuntu have issues even on fully certified laptops, and openSUSE has been pretty plug and play for me on a secondary machine even with its faster update cycle. Might be worth checking your hardware too, as random hitches and reboots could indicate that you might need to reseat RAM or that the CPU/GPU is for whatever reason unstable.