candidate has been updated to a more recent release of Mesa. This snap provides Mesa to a range of IoT graphics snaps including Ubuntu Frame.
You may be using mesa-core20 indirectly as it is a content snap, not an application. To check run the following command will list any snaps using it:
snap connections mesa-core20
To test, just switch to the
snap refresh --candidate mesa-core20
And use as normal. Please let us know any results here.
If no problems are identified we aim to promote to stable in a week.