Stereo. I have a new 55" Spectre from Walmart, 2K but never use it, and its sound is good, and stereo. I’ve tried computer 3.1 system on my last TV (sound was low on it) and it always had buzzes and hums.
Now that I get all my TV over the net I am guessing I get stereo mostly. I will say it sometimes gets out of sync and requires wifi/device/app reboots, but the experience is satisfying. I just got Britbox app for 6.99/month and I have all Doctor Who, Blackadder, Red Dwarf, Mr. Bean, Keeping Up Appearances, amongst all the rest. I find watching Tom Baker now is crystal clear, like seeing them for the first time. And no commercials!
I went with Youtube TV because of its unlimited cloud DVR for 9 months. Now I just record everything and try to watch it before it drops off, and I never delete anything.
However, I have heard 5.1 systems, and they are movie theatre cool. I might set one up one day, it could be like watching all the shows for the first time again!