I'm having frequent troubles with sound on my TCL Roku TV (65" - 2020) and my Roku Ultra. Symptoms are that after starting a channel or pausing a program (I use YouTube TV a lot, but it occurs on other channels such as Netflix) sound does not come on. Ofter its a 3-5 second delay, but ofter it never comes back. I generally find that I have to pause the program and restart it. This generally results in the sound coming back. Occasionally (very occasionally fortunately), I end up having to shut off the TV or Ultra and restart it. This fixes the sound for awhile.
Set up is TCL connected to a Yamaha Amp via an HDMI ARC connection - this works great most of the time except when I have the sound issue described above.
The Roku Ultra is connected to a Visio TV with sound output to an external bluetooth speaker - however I have the speaker hardwired to the TV using component output from the TV to the speaker.
Behavior between the two Roku's seems pretty much the same. I have sound leveling off on both Roku's
Seems to happen on any channel. Had it happen again on my Ultra just the other day upon turning my TV - The Ultra is powered separately and is on all of the time. Ended up restarting the Ultra to get sound back.