The closest free alternative to Trello would be Planka, IMHO. It works really well (rock stable, quick, painless), is pretty and doesn’t need much resources. The only thing I miss (which Trello also lacks, btw) is the ability to have subtasks in the way Jira allows them; for this, Plane or Leantime might be good candidates (I haven’t used either of them yet, though).
The admins are probably ignorant sluts, I guess.