How to only get RecordingID from MusicBrainz?

[LyricsLover]

If you don't want to to deselect the options in the GUI like this:

then you have to modify the used Websource Script.
Create a copy from the original file, open this copy in a texteditor and write every unwanted tag like this
set ARTIST
set TITLE
set ALBUM
...
at the end of the Websource Script. Then use/call this modified script from Mp3tag.

BTW:
There is no MusicBrainz-Tag called "RecordingID" AFAIK
MusicBrainz knows
MUSICBRAINZ_TRACKID
or
MUSICBRAINZ_RELEASETRACKID

Please see also this:

MusicBrainz Recording IDs erroneously written to MusicBrainz Track IDs

The definitive source for lookup of Picard tag field names is https://picard.musicbrainz.org/docs/mappings/ From there it becomes clear, that what you refer to as bug2 above is intended behavior: what's displayed as "MusicBrainz Recording Id" in Picard is in fact written as UFID://musicbrainz.org (or MUSICBRAINZ_TRACKID for non-ID3v2 tagging formats). In Mp3tag it's simply MUSICBRAINZ_TRACKID as listed in the overview table at Add mappings for more MusicBrainz tags Let me know if I'm missing …