To check the theory about the Ubuntu-specific patches, I tried to boot another Linux distro (Fedora Live 35) in order to see if the problem would exist: it did not.
The kernel used was: 5.14.10-300.fc35.x86_64.
Which is more recent that the kernel 5.13.0-20, currently used by Ubuntu 21.10. Therefore, it looks that both the older Ubuntu-specific kernel and the newest Fedora kernel do _not_ have the problem, thanks to some custom patches that (apparently) do _not_ exist in 5.13.0-19 nor in the mainstream Linux kernel.
It's getting even more tricky.
An alternative long-shot theory is that thermal management policies changed in the newest Ubuntu, but does not activate with kernel 5.11 because of the lack of some kernel feature. That would explain why the problem exists with the mainstream kernel as well, but not on another distro.
To check the theory about the Ubuntu-specific patches, I tried to boot another Linux distro (Fedora Live 35) in order to see if the problem would exist: it did not.
The kernel used was: 5.14.10- 300.fc35. x86_64.
Which is more recent that the kernel 5.13.0-20, currently used by Ubuntu 21.10. Therefore, it looks that both the older Ubuntu-specific kernel and the newest Fedora kernel do _not_ have the problem, thanks to some custom patches that (apparently) do _not_ exist in 5.13.0-19 nor in the mainstream Linux kernel.
It's getting even more tricky.
An alternative long-shot theory is that thermal management policies changed in the newest Ubuntu, but does not activate with kernel 5.11 because of the lack of some kernel feature. That would explain why the problem exists with the mainstream kernel as well, but not on another distro.