I can onfirm.
On my WiiM Ultra, latest official firmware, and latest Android app as of Jan 02, 2026, this problem is still there.
I can play tracks from Tidal in three different ways:
1. TIDAL app, and output to WiiMUltra via TIDAL connect, My Music, Playlists: Normal volume.
2. WiiM Home App, Favorites, same TIDAL playlist as a preset: Normal volume.
3. WiiM Home App, Browse, Music Services, TIDAL, Collection, same Playlist: Volume 10dB down.
On the WiiM, I'm using fixed volume output. I can clearly hear the volume differences reportet above, and I can see them on the VU meter, both original signal and output volume.
Anyone else? Is this a known bug or feature? Where to submit a service request to WiiM?
Practical approach is not to use the TIDAL connect part integrated in the WiiM Home App.
And yes, anything else there than "Custom mixes" is completely uncustomized to my music style.