I found the Youtuber Critcal Rocket:
https://www.youtube.com/channel/UCMpEn1nKT6E_gt75GDK9IJA (https://www.youtube.com/channel/UCMpEn1nKT6E_gt75GDK9IJA)
He has a series named LoreWarrior that gives background infos on stuff from Battletech. This is for example different factions, clans, the Star League and so on. The episodes are not so long, but I find the story about the Star League is nicely read.
I can recommend it. (y)