You can do what I do and press mute before you launch Youtube. I don't use it enough to bother looking for a setting within the channel/app, but that's up to Google/Youtube.
Hi @quantumus,
Welcome to the Roku Community!
We understand that you're having issues with the YouTube TV channel, and we would be more than glad to look into this and assist you. Could you please specify the issue you're experiencing? Also, is this issue isolated, or are other channels also affected?
Once information is received on our end, we'll be able to investigate the issue.
All the best,
Kash