Ohhh I only just found this thread through the “related” or linked button on the forum - still didnt read all.
Just wanted to drop this here: [Issue] FW13 Fedora 41/42 (kernel 6.14) hard freeze - #15 by thedaniel
In my case, with iGPU memory set to just 0.5 GB and a decent amount of screen real estate, I can pretty easily reproduce the issue. Yesterday I had three boots in a row with glitches and freezes within ~2 minutes of boot each time - partially also freezing and gpu restarts from what it felt like - running Ubuntu with the latest mainline 6.14 kernel.
What i do after boot - you could consider a stress test maybe - start browsers up [3-4 profiles], started a youtube video [laptop and chrome is setup to use hardware decode] in one of the tabs from last session. Start some dev tools of which some take 10+ threads full cpu for some minutes, containers etc - system basically goes to ~10GB memory used very quickly.