"This support can't be socketed into this skill" for skeleton minion skills

ref. 3,806,177,122.

As of today, every minion skeleton skill that I have (and I have a lot of them due to muster support on my main minion skill) greys out supports of any kind with the message "This support can't be socketed into this skill".

Tried re-logging, changing zones. Didn't do anything. I have enough attributes for both str and int supports, but no matter the minion gem tag - be it attack or spell (e.g. reaver vs storm skelly), the entire list of supports is not usable according to the game.