For quite some time now I got this error when logging in with any char and having Plater (latest version) installed and acitve:

Message: Interface\AddOns\Plater\Plater-Plater-1.13.5.91-Classic.lua:8031: attempt to call method 'RemoveRule' (a nil value)
Time: Mon Oct 12 08:23:13 2020
Count: 1
Stack: Interface\AddOns\Plater\Plater-Plater-1.13.5.91-Classic.lua:8031: attempt to call method 'RemoveRule' (a nil value)

Locals:

I though maybe this gonna be resolved some time, but maybe noone being aware about this?

Ok, thx. Opened one in the other repo, will close this here.
But afaik it is not related to not using the latest version, I always update via Twitch and Weakauras companion app.

Please check your Masque installation. Sounds to me like you're using an outdated version.
And please use the classic repo for classic issues: https://github.com/Tercioo/Plater-Nameplates-Classic