Why isn’t building a modular A/V receiver a thing, then? Not only it would allow to stay up to date with all the current audio standards, it would allow to update the sound cards and amplifiers independently as the needs change.
Meanwhile we’re pretty much forced to upgrade our receivers every couple years because they don’t update them to support new standards — like the Dolby Vision, which a receiver merely needs to pass through to a TV/projector(!).
https://arstechnica.com/gadgets/2024/02/hdmi-forum-to-amd-no...
Also, many people presumably do use a PC as a media server. But, I imagine one would still output that to "real" audio and/or video equipment, if one has a listening/viewing setup that warrants it.
Also, I think there are plenty of open source audio amplifier projects. That simpler problem is not exactly applicable to the OP, though, and not subject to the same licensing and chip availability issues as a full blown AV receiver, apparently.
[0] https://www.audiosciencereview.com/forum/index.php?threads/o...