I have both now a few days in operation and basically it does what I want, it displays the ratings no matter what tag-standard. there are a lot of setting options which I would like to adjust to my needs. thanks for the plugin suggestions.
In another way, LMS offers to display ratings by default without using an additional plugin.
so I thought there was something wrong with my mp3 files, or I was tagging wrong in MusicBee.
How a non-working
mp3 rating is looking in LMS:
and how the working
Flac rating looks: