This is from 2023, but this might still be a good read on how to get to a very low watt idle build, there’s a few more post on other older builds on that blog as well: https://mattgadient.com/7-watts-idle-on-intel-12th-13th-gen-the-foundation-for-building-a-low-power-server-nas/

The Linux Foundation has a mentorship programme which is really great, might be worth a look, although I am not sure how easy it is to get accepted: https://docs.linuxfoundation.org/lfx/mentorship/mentees

Use Clevis either with TPM or Tang (remote server) https://github.com/latchset/clevis