Since it took me a lot of time to browse forums and test platforms, I would like to share my experience here:

Configuration:
1) Laptop with Windows 10 Pro 22H2
2) "Qobuz Studio" 1 Month tryal, then € 14,99 incl. VAT! / month (chosed this one to be able to quit monthly)
3) "Qobuz" bottom right audio out = 'ASIO Fireface USB'
4) PC > USB > "Babyface Pro" (the old one, NOT FS)
5) "TotalMixFx": Signal at 'SOFTWARE PLAYBACK AN 1/2', routed to 'HARDWARE OUTPUT AN 1/2' + 'MAIN' = 'PH 3/4'
a) 'AN 1/2' = via XLR directly to monitors
b) 'PH 3/4' = directly plugged headphones with low impedance (6,35mm audio jack, because +13 dBu > +7 dBu)
c) Alternative: PH 3/4 via 6,35mm audio jack (because unbalanced) + 2 x cinch to my old amplifier > input AUX

Remarks:
Originally I was looking for a platform to buy CDs, but then I discovered the streaming platforms where you can also buy CDs.
I spent many hours browsing forums and tested a number of platforms, especially the actual quality of the sound, the compatibility of the formats and the operation of ASIO for my Babyface Pro.

Tested:
Qobus - min. CD quality up to "real" HiRes; e.g. 96 kHz 24 bit
TIDAL - only MQA; cannot play
HDtracks (territorial restrictions)
chandos.net - with £ 19 for a Mahler symphony relatively expensive
ProStudioMasters - was not sure about quality
Linn Records - "Subscription not available".
HIGHRESAUDIO - did not convince me
eClassical - 20$ for one CD expensive
WOM World Of Music - Not for my taste
... and a few more

What else I noticed:
It seems that the platforms also depend on which labels they sign contracts with; small ones are cheaper and thus the selection is also much more limited.
Further, I recommend paying attention to whether it is a stable platform before you pay anything - some I have called, but the website did not exist any more. In the forums then financial problems are mentioned; whether this is true, I do not know.
Ultimately, you have to pay attention to the actual quality. In some tests where the format was "scaled up", I heard exactly how the needle was placed on the turntable with my Babyface and AKG headphones. The quality was accordingly - "HiRes" is of no use there.

My personal, subjective summary = Qobus Studio / month:
- Compatible formats and playable with ASIO
- One month free trial with full functionality
- A huge selection (e.g. several album versions with the same Mahler symphony)
- At least CD- and many with higher quality
- You can listen to albums offline without buying them (but I haven't tried it yet)
- The original approach of buying CDs at all no longer exists
- More music than I can ever listen to - for 15 € per month
- You can do extremely much, but in the end - I think - only your own ears count

I really hope someone can help my experience and am eager to hear any feedback!