I had Optus and Peacock this season.
With Optus I couldn't fix the buffering. I tried multiple different VPN's and DNS services on my 500Mbit VM internet but nothing seemed to fix it.
Peacock was good, but obviously doesn't cover every game. Streams were good quality most of the time, but the only downside was goal rush had a lower frame rate than the live games for some reason which was a mess! Hopefully they fix that for next season.