Once you have all your music ripped to hard drives, you can then use a PC for playback with a direction connection to your AV receiver. You can use a keyboard mouse and software running on the PC for playback, or you can try using an outboard device for playback which offers a more standard remote control.
The biggest advantage with music only devices, like Sonos (or Bluesound) is that they are built to use a smart phone as the interface. The flip side to using a PC as the interface is that the TV has to be on so you can start the music playing. But, once a playlist is started, you can turn it back off.
I'm not completely sure, but I believe a player like Plex may offer you the same type of user interface and it supports FLAC playback. So, you could have your entire CD collection on a local hard drive of any computer of your choice, and it will play back into your system. The computer will live local to the A/V receiver and just be plugged in via HDMI.
So, you can use a old laptop or buy a small form factor PC or build something specific.
The cool part is that Plex will manage everything automatically. So, as you add music to the computer, it will be a part of your collection automatically with cover art and the rest. If you want to play back the music elsewhere in your home on other devices, you can do so. You can play it back from your phone anywhere in the world. Your family or even friends can have access if you want to give them that access.
I use Plex for my video playback of local movies and tv shows along with my music collection. While I don't have the PC tied directly to my receiver, I can playback any of it through my Roku player. I'm not sure if the Plex doesn't transcode (convert) the lossless to .mp3 format for playback on my Roku. But, direct from the PC it supports lossless formats natively for playback.
https://support.plex.tv/articles/203824396-what-media-formats-are-supported/
Literally, if you have a laptop at home, you could rip a few discs, load Plex, and try it out today for free. That's kind of what I did to just get a feel for what it was like.