Is the Mytek Brooklyn Bridge or Lumin D2 good buys in 2021?

The D2 will sound better with age, just leave it streaming music for a few weeks.
It also has a small screen as the info is on the control app, it also has an option to turn if off.

Id separate the streamer from the DAC if it was me. 

I'd go for the lumin u1 mini + denafrips ares/pontus

or 

sonore opticalrendu/ultrarendu + denafrips ares/pontus

note: this is based on my research only as i'm also looking for a good streamer/dac

@helloitsben, re: Roon, it runs on top of Tidal. I am a longtime Tidal user and still love the service. But run Roon on top of it and you’ll rarely ever find a need to use the Tidal app again. 
I use a LUMIN U2 mini as a streamer and a Brooklyn DAC+ as my pre and it’s an excellent combo. Separating the streamer from the DAC gives you more options in the long run. 

If you are leaning towards Lumin, I should probably share my less than stellar experience with their app.
Almost every time I use it, it will back out of Tidal, or the Lumin app will crash altogether. Yessss, it’s updated, unplugged/rebooted (network & streamer), hard wired connection, new switch, router, NAS, modem, Supra Ethernet cable blah blah. No change. I have Bluesound equipment in another system (on the same network) with absolutely zero problems- even when I use Tidal through their app. Opinions may differ, but for me, Bluesound’s app is where it’s at! Reliable and easy to see info with an intuitive user interface. Lumin’s app is nowhere near as reliable as or intuitive as Bluesound’s app (for me). I’ve tried different, older iPads, newer iPads, iPhone 6, new iPhone12pro: nothing has made a difference. Lumin app does not work well with Tidal (for me). I went so far as to purchase a 2nd Lumin streamer to see if that was the problem. No change. Im not a horizontal-scrollin’ Roon fan at all, but I might be soon. I’ve just about had it with the slow, laggy and crash-prone Lumin app. 
YRMV

I have used a LUMIN D1 for 5 years - it ran flawlessly - it uses the Wolfson DAC / got constant updates on the software  on the internet from LUMIN- when MQA came out my D1 could fully unfold the files at no extra cost - definitely heard an improvement in my sound. I stream Tidal HiFi .  I sold the D1 5 months ago and now I run the LUMIN T2 in my main system / it runs a Sabre DAC - bigger sound stage and more detail than my D1. I just added a LUMIN D2 for my second system in the Mancave - love the LUMIN D2 - the Wolfson DAC has a warmer sound - vocals are great with the D2. Build quality on LUMIN streamer / DACs is great - software support is great - both the T2 and D2 are improving in sound as they break in.
just my 2 cents - Happy Listening!