Hahahaha welcome to Snaps.

Get rid of Kubuntu is what I would recommend. Really.

Question, do you want to do crazy stuff? Do you want A LOT more than what you find on Flathub.org ?

If not, and you want a fast and stable system, get Fedora Kinoite, you may want to use Universalblue Images to have Firefox and all the rest working (videocodecs installed and automatic updates mostly. If you have NVIDIA you NEED the ublue kinoite-nvidia image)

On Fedora you just need to disable fedora flatpaks, enable flathub, install your apps and voila.

Follow the flathub.org Setup instructions, in Discover you can set the sources and disable Fedora Flatpaks.

I am working on a GUI setup script to fix everything.

Just a guess: you might actually be running the CPU at a low frequency. As in the frequency scaling driver isn't working.

Maybe poke around on a performance monitor tool. Seems like there's "Plasma System Monitor" on KDE. Make sure the tool can see all the RAM, all of the CPU cores (2x physical cores with Intel hyper threading).

It should also report the CPU frequency, which should go up and down depending on the load. You can also check that the CPU temperature report is reasonable.

This also gives you process info, so when one of these 5 second freezes happens, you should be able to see what shoots to the top of the list. Or maybe there's a background task churning through a bunch of stuff. Or maybe the flash access is really slow.

Why is this getting down voted? It's a genuine ask for help :/

In addition to the CPU throttling itself due to thermals like you said, you should also be aware that all Ubuntu's are replacing more and more traditional packages with snaps for an increasing number of applications.

Step 1 (by the system) of opening a snap application for the first time (since boot) is to extract the compressed snap image, which makes startup time significantly longer (like several seconds for something you would expect to be instant). Once the application is started performance should be the same as if the application had been installed as a traditional .deb package.

You should also consider adding flatpak support and flathub. Applications installed as Flatpaks generally integrate better in the desktop than snaps, and flathub has a large and growing selection of apps. The flathub website has a few command lines you can copy-paste to enable flatpak and flathub support, then apps from Flathub will show up in the Discover app store.

Personally I use Kubuntu and use both Flatpak and snap apps, but generally prefer flatpaks when they're available. And any software where I don't care about having a recent version I install as a traditional package because it's more lean

Welcome to snaptown where everything is slow at first. Please consider not using a canonical Linux distribution (Ubuntu, Kubuntu, Xubuntu, Ubuntu Studio). So something like Linux Mint, Fedora Linux.

You said you want to do gaming? Consider Garuda Linux (with KDE flavour) or Nobara Linux (Gnome flavour) those are aimed for gaming but supports everything else as well.

Snaps are only really useful on Server Machines and I don't know why, canonical is pushing this so hard.

THe good thing with linux, that it's totally transparent, you can easily find what's wrong, if you look at the right place.

First I would check journalctl, dmesg, running processes with htop, if I can see something wrong, unexpected. Check hard drive smart and run short selft test with gsmartcontrol.

Here is a general troubleshooting guide from arch wiki: https://wiki.archlinux.org/title/General_troubleshooting I know you use ubuntu, but most of the commands here are the same on all distros, basically anything not related to pacman should be the same on your system

Ubuntu wiki has a similar guide, but shorter, guide, maybe start here: https://help.ubuntu.com/community/TroubleShootingGuide

If this isn't your first round on linux, Try Debian, set it to use non-free contrib packages and set the appstore to install apps as flatpaks before native.

Avoid using Ubuntu based distros as they run Snap packages which are just a general nightmare for users.

Snaps make sense for servers, but the only reason Ubuntu forces it on users is $$$$.

This sounds like a slow drive except you said it's on an m.2. If you just switched recently enough that this wouldn't be a major inconvenience, I would try a different distro. You haven't said anything about your use case, so I can't make a specific recommendation, but distrochooser.de could help with that.

I had this problem too.

The issue for me was that my computer had two disks, a small fast one (sata ssd) and a large slow one. Windows had separated itself with the operating system itself and installed programs on the ssd, with all user documents on the slow disk.

Linux can do this too. Put a partition mounted on / (root) on the fast disk, and one mounted on /home on the large disk.

I’d put both on the large disc initially.

There’s a part of the installation where you set up the partitioning. Redoing the installation really sped up my Linux Mint installation.