it stands up to stress/linpack, I've the flirc case & and official adapter. It may be something to do with trying to accelerate video. Otherwise it has never crashed.
I suspect it's a compilation flag that this ubuntu distro has set correctly that RpiOS has not, I also see some about:config messing to try for another time.
AKA, use one of the official power adapters, and one of the large 3rd party heatsink/fan combos.
Web browsing on the rpi is painful at best, and when its "working" will be stressing the poor thing to its max, so... see above.