Maximum CPU frequency reported wrong by lscpu, CPU not boosting to actual maximum frequency

I'm using Ubuntu 20.04, and my CPU model is the Intel i7-10750H:

> lscpu
Model name:                      Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz
Stepping:                        2
Frequency boost:                 enabled
CPU MHz:                         800.000
CPU max MHz:                     2601.0000
CPU min MHz:                     800.0000

This processor has a maximum frequency of 5 GHz, not 2.6. The frequency never exceeds 2.6 GHz, even when playing graphics-intensive games. The stuttering is noticeable.

On my other laptop, with the same Ubuntu version, the boosting mode worked out of the box. How can I un-lame my lame computer?

Update

cat /sys/devices/system/cpu/cpufreq/boost returns 1, so turbo boost should be enabled.

cpupower frequency-set --max 5000Mhz has no effect.

Update 2

Setting GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force", updating grub and rebooting now shows

Model name:                      Intel(R) Core(TM) i7-10750H CPU @ 2.60GHz
Stepping:                        2
CPU MHz:                         2600.000
CPU max MHz:                     5000.0000
CPU min MHz:                     800.0000

with CPU freq often stuck at 2600 MHz.

And here's a little test, showing that it never reaches the 5000 MHz:

> stress -t 30 -c 20 -i 20 -m 20 &
                        while true

                            lscpu | grep "CPU MHz:"

                            sleep 2
                        end
stress: info: [2900] dispatching hogs: 20 cpu, 20 io, 20 vm, 0 hdd
CPU MHz:                         1506.625
CPU MHz:                         3499.999
CPU MHz:                         3599.998
CPU MHz:                         3511.052
CPU MHz:                         3599.481
CPU MHz:                         3574.137
CPU MHz:                         3505.161
CPU MHz:                         3532.195
CPU MHz:                         3579.484
CPU MHz:                         3578.953
CPU MHz:                         3500.001
CPU MHz:                         3500.000
CPU MHz:                         3591.847
CPU MHz:                         3544.761
CPU MHz:                         3500.000
stress: info: [2900] successful run completed in 31s
CPU MHz:                         2600.000
CPU MHz:                         2600.000