Other options are LUKS with Tang and Clevis, or LUKS with SSH and Dropbear.

Sorry, I have no details.

Edit: Tang/Clevis are local software and a network server that provide keys. If stolen, won’t boot.

SSH and Dropbear make it so you can login to provide keys.

It is complicated. There are several options, each with tradeoffs in functionality, compatible software, and performance.

A simple method is to use one system as a desktop, and SSH into the others as “headless”.

Other options include making a K8s or HPC cluster (there are other cluster types).

Spreading a single set of communicating processes requires a low latency interconnect. Something better than Ethernet, like Infiniband. But many programs don’t support that.

What features do you want?

What should my first configurations and preparations

Write on paper your goals. Write on paper a list of your systems and what needs to speak with what.

Then pick the most important or simplest device and get it connected the way you want.

At home, colors Whatever color the purpose is.