okay, I found where past me got stumped last time with this box:

`echo 0 > /sys/devices/system/cpu/intel_pstate/no_turbo`

this fails when run as root in Debian 13, even with Secure Boot disabled, Kernel Lockdown disabled, etc.

in dmesg there's a message

intel_pstate: Turbo disabled by BIOS or unavailable on processor

this is because the #Dell BIOS is disabling turbo due to running on a "non-genuine" power adapter. I was able to work around this in Debian 12 but so far the same tricks aren't sufficient in Debian 13.