Hi, HiMacX. I am not using vinyls at all, so for me it makes absolutely no difference. But being quite deeply into hi-fi hobby I would guess that WiiM's omission of turntable pre-amp might be based on the following logics: (i) if you are serious about the vinyls you would probably have your own phono pre-amp well-matched with your expensive turntable - the one built into $500 all-in-one would simply be not good enough... so: you would not need it in WiiM, (ii) if you are just a casual user then most likely your turntable would have built-in pre-amp (still probably better - due to the synergies - than the one they could put into all-in-one amp), so... you would not need it in WiiM. For me this makes sense - I would not be a fan of adding (for objective reasons: not-so-great?) phone amp and likely: increasing cost / price of the unit.
EDIT: But if you need the phono pre-amp then probably you could consider buying WiiM Ultra streamer + Vibelink - it would have all the inputs you may need and sound-wise is reportedly quite similar to WiiM Amp Ultra. But then you have two boxes not one, which I personally would not like...