aside from stuff like annas archive / libgen

in the past, i had ok luck using dht search sites like bt4g (org) but it was very hit and even more miss in terms of whether the torrent/magnet still had seeds. but that approach did have some collections like what you mentioned. and i did used to get the occasional valid collection mixed in among the dead torrents and other bs.

i havent really done it that way in a long time so not sure how well it works these days tho... like I searched a couple things similar to what you had in the OP and did get some small number of results (less than 1 page). some of those appeared valid but watch out cuz there were also some obvious malware ones that were like <title>.exe. Probably not the best way to do things for 2026+ ... and if you try it anyway, i highly recommend an adblocker, an up-to-date torrent client like qbittorrent, and maybe run a antivirus scan on the download when it gets done just to be safe.

could also check https://fmhy.net/reading but i suspect most of those are also going to be geared more towards individual books than collections. Only other things I can think of are usenet/debrid but I don't have experience w either so I couldn't say definitively.

If you do manage to find a good modern way to get collections, I'd also be interested to hear it.