Your / (root) shows 89% usage; or, at least it did at the time of the inxi output posted earlier. I note also that your /home is not on a separate partition, so its contents too are included in that percentage. Add the dynamic zswap file to the mix, and your entire / utilization is fairly high.
What I’m suggesting here is that all these factors combined may contribute to a progressive slowing down as more data is written to both system and user caches, and the swap file is increased in size while using your favourite apps over a period of time. As the amount(s) of available space decreases, so does the performance.
Only you best know your system, however, if this indeed is causing it, there are a few possible resolutions;
Clean your system; empty caches; rid yourself of any unwanted junk; or packages you never use.
Offload larger less frequently used personal data to an external USB drive; ISO files and movies, for example.
Buy a larger SSD for use with Manjaro: I find a 1TB disk is usually sufficient; but it would depend on your needs.
Buy another SSD for /home: I generally suggest a separate partition for /home but a separate disk could be beneficial in this case.
It doesn’t seem much different from what I can see.
Are you a Steam Gamer? If so, maybe some of those games are taking up a lot of space; some of the downloaded data for games can be 10G+ each.
You’re using Snap apps - using the Official Repository version of some of these would also save an amount of space; even .appimage or .flatpak might be more performant; and certainly allow better security than Snap (but that’s not relevant to the topic).
I would prefer as much unused space as possible; perhaps a total utilization of 75% (approx); but only you can know how much you can comfortably work with.
Create more space if you can, and see how it then performs through the week. If you feel the system slowing again, compare the usage % when it happens.
That’s all I can suggest. Let us know if it seems to make any difference.
I just switched from X11 to Wayland, there was a dropdown on the login screen where I could choose one of those (didn’t know about this feature). Right away the system feels instand and snappy. I have been working for an hour now, but I am confident this solved the issue(s) since it feeld really fast and stable.
I want to thank everybody who have contributed with answers and suggestions! Very much appreciated!
Btw: is it possible fonts are rendered a bit different in Wayland? I notice some difference in some apps. They seem a bit fuzzy compared to before. But it can also be that I need to adjust to the (minor) changes, I am not sure.
Yes. I recall this was mentioned a few times recently. Search the forum and you may find the relevant threads. I didn’t pay much attention to it, despite using Wayland myself, as I hadn’t noticed any font blurring and presumed it must have been Nvidia related (as so many issues seem to be).