I think you're missing the forest for the trees here.
PeerTube accounts are for video makers, not video watchers. If I want to watch a PT video, I can do so without an account. If I want to leave a like or comment, I'll do so from my mastodon or misskey account. The reason Peertube servers don't tend to federate with each other is because they don't need to: they federate with mastodon/misskey/pleroma servers for the people who want to watch. (also, the https://spectra.video/about/follows page OP linked seems to ignore non-peertube follows?)
As for finding new videos on PeerTube, I recommend using sepiasearch.org