Streaming

Yes - a Raspberry Pi running Ropieee. Less than £80 and serves up excellent USB out if you get the latest version 4. Running it with a Khadas Tone Board with Roon and the combination is brilliant. (Remember that inside some £x,000 streamers you will find it’s an R-Pi doing the work). My son has far better, and younger, ears than I do and he assured me that an A/B test vs a Node 2! is an easy win for R-Pi plus Khadas. I had to talk my ears into hearing a difference, and they obeyed in the end - but that could be my optimism bias from having saved £300.

I tried Deezer HiFi ($20/month) and found the sound quality was quite good, on par with Tidal, but the lack of gapless was really annoying. If Tidal fails I'll go back to Deezer despite it's shortcomings. 

A lot of things in the press notably financial issues are worrying for the longevity of Tidal as it stands under present ownership.
To the OP.
I have just ( 6 days ago) signed up for Deezer as an alternative to my Tidal as they were offering the first 3 months of premium+ at just $0.99 each month so a no brainer. So far I am pretty impressed, no they do not offer the MQA masters but at $9.99 regular they match Tidal regular 16/44 service with what seems to me at least a good as choice of music
.And they have a Pandora-esque feature called Flow that plays endlessly based on your tastes and saved favourites.
Give it a try via Bluesound Node 2 or Vault 2. Boht have digital outputs so bypassing their own built in DAC, which is how I use my Vault, digital coax sent to my Lyngdorf 2170

What makes you think Tidal may go belly up?

I’m looking to deezer Hi-Fi in case Tidal goes belly up

Node 2 has digital outs so you can use your external dac.  You can use the analog and digital outs at the same time.  Connected to separate inputs on your preamp you can compare and enjoy a different experience between the two dacs.

Does it play straight to the DAC?

It’s technically not “dedicated” since it does include a (built-in) DAC. But close enough, nonetheless.

Yes

Bluesound Node 2.