Seems like Piped and Invidious are both on their last legs. Public instances on both services are pretty iffy, they go down fairly often now. Freetube works well on desktop but no real way to sync subscriptions and watch history to a phone. Self-hosting Piped/Invidious might be the solution but I don’t know if it’s worth the upkeep when YouTube is actively fighting against it.
Libretube seem to offer multiple instances ?
Kavin.rocks seems stable, so far.
the problem seem to be about finding reliable instances, so u could self host if u have run out of options