Fedora 33 freezes frequently and randomly while watching video (FireFox and Chrome). Small sound sequence loops endlessly. All input / output devices are blocked, no mouse (laser off), no keyboard (caps lock LED does not work). The only thing that helps is hard reboot. No error reporting after the hard reboot.
My machine is Dell 3640, intel 10700k. Comet Lake PCH-H W480 chipset. No discrete graphics card.
Check your GNOME shell extensions, I had to turn off Freon to stop this from happening on my NVIDIA rig.
I have only 2 extensions active. Background logo and Dash to dock.
Just deactivate them and see if this happens again.
Can someone explain to me how a gnome extension can block (without kernel panic) an entire modern and supposedly “multitasking” system?
What’s going on? How can I trace what happens just before and after freeze and hard reboot? Probably a watchdog to activate? I’m sorry, but I’m from macOS and my knowledge of Linux is limited.
Extensions many times are made from enthusiasts or developers who have an idea independent being a part of the gnome development team. Then things change and the extension has to follow this changes. This can cause hick-ups and problems.
And to find out the bug/problem, it’s needed to switch of extensions to see if the problem still exists. As it is not possible to deactivate the OS and just run the extensions we have to do it the opposite 
We are still waiting that you give us a feedback if the problem is gone after deactivating the extensions.
Waiting for me?
No sorry you asked him @vvot to deactivate the extensions … but til now he not gave answer, just asked why an extension could make troubles.
I had a very similar issue to yours and later found out that the CPU had a quality defect. (BTW, this CPU has been running windows for three years without any problems 
)
After replacing the CPU, all problems were solved.
I had this problem too, and Fedora only work by kernel 5.10.14 and Fedora Freez on kernel 5.10.18 and 5.10.17 ,
only work fine by kernel 5.10.14
I use Fedora 33 by Gnome 33 and Fedora installed on Lenevo Thinkpad e590 with 4GB of RAM
and HDD no SSD
I also have this problem with fedora 33 Gnome recently, with Firefox and Chromium tabs crashing… (I’m on the 5.10.19 kernel and have the fractional scaling activated)
I tried to work on Windows (several weeks), the system was stable, no problems at all. I went back to Fedora 33, updated the system, for the moment everything is perfectly stable (with extensions), fingers crossed. I do not believe at all that the problem could come from an extension. If a process in “user land” can crash kernel, we have a huge general stability problem (nothing to do with extensions) …
Another freeze of death 
, sigh…
when the freeze occur, just switch via CTRL+ALT+F3 to an terminal.
login and type “dmesg”
do you find something like “GPU hang” or so.
if so, your need to wait for new kernels.
You probably need to use an older kernel until the problem gets resolved. Fedora Linux keeps the latest three by default and you can select the older ones from the boot menu.
Keyboard, mouse do not work at this time. The only button that works is “on/off” 
Probably I have something similar to this:
I repeat that in my case it is the “freeze of death”, nothing works (neither keyboard nor mouse), I just have the same image on the screen and sometimes a fragment of sound which repeats endlessly, the only one solution is the hard reset. After the reboot, nothing in the system log, just a “time hole” corresponding to the freeze and reboot time.