XPS 9570 SpeedStep not working any more after BIOS Upgrade to 1.31.0

Since I upgraded the BIOS of my XPS 9570 to 1.31.0 SpeedStep does not seem to work any more. I am using Ubuntu 23.04, Kernel 6.2.0-23 (but I have the impression that the problem happens under Windows, too).

First of all, setting the CPU frequency governor does not work any more. If I set it to performance or power save does not really affect the system.

The system seems to work only in powersave mode. All CPUs are working at 800MHz, sometimes going up to 2.9GHz.

I disabled SpeedStep in BIOS: System works again, CPUs scale between 800MHz and 4.8GHz. I wondered that even when disabling SpeedStep the frequency is still changing. I assume that has to do with SpeedShift, which is still enabled in BIOS?

After hibernating and waking up, the CPUs are again in powersave mode, not using more than 2.9GHz at max.

Are there any known issues? How can I re-enable SpeedStep and control the governor powersave/balanced/performance from my OS again?

Thanks!