I can equip sentinel idol in my mage (it says require class: Sentinel)

[Karib]

the stats work (ignite chance on this idol gives ignite chance for my mage)

[Llama8]

Known bug:

Class-specific Idols usable by other classes

I found a Primalist-only idol on my primalist (vigorous large nomad idol of bonding, gives 6% increased hp & 25% damage over time), went over to my Acolyte & was able to equip & benefit from the idol (hp went up from 752 to 788). Tried it on my Mage as well & it worked on that as well.

[Hackaloken]

This has been fixed for 0.7.7. Thanks for the report!