The only way to get rid of PRIV, AENC, GEOB etc fields now is to cut and paste tags or delete tags then undo. If operating on 100s or 1000s of files at once this is not particularly safe. If something goes wrong during pasting you potentially risk losing a lot of information. Please consider an action "Remove unsupported fields" which could do the same thing one file at a time.
What do you think what are the rules to describe and detect "unsupported fields"?
In the moment when such tag fields will be supported by Mp3tag for removing they are no more "unsupported fields".
In the actions there is - Remove Fields Except.
Does this not solve your problem?
Alternatively you could try mpTrim without any trim option but it has the facility to rewrite the tags and select the grayed check boxes, if the information is there it will not be over written.
So load everything into mp3tag and save tags (Write ID3v1 selected in options - tags)
Start mptrim, Uncheck the Keep IDV3v2 tags if present, Open and let it process all your mp3s.
While you can load hundreds of mp3s into the program, it will take considerable time to process
Then you have to load the mp3s into mp3tag and save tags to get the ID3v2 tags, without any rubbish.
Messy, but you only have to do it once.
"Remove fields except" is good and I would use it but it doesn't delete unsupported fields. If this action could be changed to really remove ALL fields except the ones listed I would be happy.
I want an action that will do the same as cutting and pasting tags, but one file at a time. i.e. it would read all fields, delete the tag, then write the tag back with only the supported fields. Any fields not included in the supported fields would therefore be effectively deleted.