I use LibreTube and it looks like half of the instances keep getting shut down and then get back up, and the speeds for all are atrociously slow that it is just better to watch it on YouTube on Firefox. I heard a while ago YouTube was blocking certain Piped instances but do not know if that is the same case right now.
It’s a cat and mouse game with Google blocking the Piped proxy IP address of popular instances, and then those instances getting a new IP to use for it.
Solution is to use smaller instances or self host your own small/private instance, issue with that solution is that then the small instances become popular and the cycle continues.
On mobile some apps like LibreTube can disable the piped proxy and make a direct connection instead (which also lets Google see your IP), but I don’t know any way to disable piped proxy for public instances on PC
I think the documentation by default doesn’t federate your instance so a private instance should be as accessible as your capabilities to get it up and running.