I did try Lumin Ethernet-wired (no other way) with Eero 6 Pro Wifi-6 mesh network router. Connected to my RME by Optical digital cable. Used via Tidal Connect. I will ONLY ever use these streamers through Spotify and Tidal themselves, never their own app. (The own app is used for other settings like firmware upgrade or upsampling etc.)
I also play Limetree Bridge II with wired, but it also works flawlessly via wifi only.
Sound quality on both options was the same, running via RME to my Dynaudio speakers. But Limetree is smaller, upgrades are totally automated via web one click inside app, and optionally works completely wirelessly.
FYI - Tidal is always 44 kHz, 16 bit, with usually 1411 kbps as I have a 1 GIG wifi connection in a big city. No need for upsampling etc, although Bridge II also does upsampling with a hardware switch. I've never needed it. Sound is great without doing all this tinkering.
Limetree Bridge II it is for me. Lumin U1 I'm sure is nice I’m sure for people who don’t mind a large clunky gadget and twice the price for the same SQ.