For those interested, I finally managed to compile all the steps I’ve done in order to boot the Rockpi 4C+ with LTSP. I’ve left it at the LTSP discussion here.
Despite the guide is for booting RockPi 4C+, I think it should be applicable in any of the boards capable of doing PXE boot.
I know this is a nuance but I’d appreciate a lot if someone could check it and make same comments mostly if there is something too obviously wrong. Moreover, I’m stuck in a non mandatory step (shrinking the final SD image size) in which any help will be appreciated.