I started to write this answer:
As many users have found MC does not use all standard ID3v2 tags. I don't know why, perhaps for historical reasons. The programmers developed the system years ago.
That doesn't bother me. I use MC as my main media organizer and tagger. I use many file formats. Some of them use different tagging standards, some don't support tagging at all. I have also many custom library fields that don't exist in any standards.
It is enough for me that the most basic tags like Artist, Name, Track # and Album, use standard fields and show up correctly when the files are occasionally used with other programs or devices. ...
However, I decided to check what happens when a custom field named Original Artist is created. To my surprise, MC used the TOPE tag for it. So I was wrong.
MC supports TOPE.
Just make a new library field in
Tools > Options > Library > Add and name it exactly as Original Artist. I selected
Extended for the category, but you can choose anything you like (the field will show up in the selected category in
Action Window > Tag Info). Tick
Store in file tags (when possible) too.
You can add this new field to your views in
View > Customize Current View.
You need to do
Update Library (from tags) once for importing the field info.