I think it's morally acceptable to keep a personal archive of the embed-only private Vimeos the people you sub to on Patreon post. It's not piracy, I just know how it is to be on The Internet and how quickly large swaths of content can just be wiped out in an instant. There's people I've seen up and delete their entire portfolios off the internet, both paid and unpaid, and nobody had an archive of it all, so a lot of it just disappears. It's not piracy to save something in the event of disaster.
Anyways saving those videos is as simple as downloading a cookies.txt from your signed in browser and feeding the link to the specific Patreon post to yt-dlp.