Is there a way that I can get a script or app of some sort that will go through my YouTube subscriptions and find any PeerTube mirrors?
I believe there is an option for that.
https://docs.joinpeertube.org/use/channel-sync
But it has to be enabled by the admin.
think what they meant is, that if some existing creator has channel on peertube, or someone is unofficially mirroring (for exaample brodie robertson, or this week tonight). The answer afaik is no. The number of creators present is very small, and hence no interest in automation. You can try to find your creator through https://sepiasearch.org/ but that is about it
You can also search on any peertube instance in the search bar and if it’s connected, it will search the same content sepia search uses.
but this depends on the version that the instance uses, and not all versions suppport it, only newer ones do, so it is a thing for eventual future