It’s just a zip file with a different file extension. Zip a stack of jpegs with filenames that will list them in reading order when sorted alphabetically and then change the extension.
I’ve been using 1Blocker for years. It used to be a one-time purchase, but now it’s free with many features requiring a subscription.
I do subscribe, though. It’s updated frequently, can block trackers in apps, and syncs settings across all my devices. Its comment block feature has probably kept me sane.
https://apps.apple.com/us/app/1blocker-ad-blocker/id1365531024
Microsoft’s Exchange Online Plan 1 is email-only and is 4/month per user. There are probably cheaper IMAP providers, but EO1 is full exchange: mail, global address book, calendars, etc.
Jellyfin has more functionality but is a lot more technical to set up. I didn’t think it was worth the effort since I already have a Plex server running, but I could see going through that if I didn’t.
Been running Plex with a lifetime pass for around a decade. Worth it for me for sure.
You are not the only person who just uses Subscriptions. I do, too.
And I am considering using rss to track channel updates instead of Subscriptions so I can see what’s new without going to YouTube directly. Less likely to get hit by distractions.