This doesn't answer your main question but I suspect their thinking is that VPN use is already very common in torrent communities. So common that it's not really a big deal for users to browse the site via VPN if necessary. It's not really that the staff there is going to do age verification, realistically if necessary they'd likely just block access from whatever states/jurisdictions are giving them issues with age verification.
That aside not too sure if what you're looking for currently exists. There are a few general torrent sites that also operate Tor / I2P domains, and also the general torrent indexer Postman exists on I2P. The amount of users in Tor / I2P networks is way lower vs the clearnet torrent sites so a hyper-focused torrent site in Tor / I2P doesn't seem viable but I could be wrong.
Never needed to use this but have seen that tools like https://github.com/fedarovich/qbittorrent-cli are able to export lists of loaded torrents in various formats, it might do what you want.
e.g. if you're going to load the output in LibreCalc then you probably want to export a list in csv format most likely (the project's wiki mentions it https://github.com/fedarovich/qbittorrent-cli/wiki/Output-Formats).
Something to consider for the future, you could re-work how you are storing your torrent data and hardlink all those cross-seeding torrents in their own folders. So if you do a full delete of one torrent + data it won't actually affect the torrent + data of other torrents. If you have it split out like that then you could even try to automate the whole process of deleting old torrents with tools like https://github.com/Hundter/qBittorrent-Ratio-Manager or https://github.com/Mythic82/Qbittorrent-auto-delete
On Linux it would be something like
Would hardlink the same torrent data in two places so that torrents for trackera can point to the trackera folder and torrents for trackerb can point to the trackerb folder.