I've personally been working around this using a custom fork that messes around with the simultaneous connections settings of the webtorrent library, and it seems to help a bit, but I still get freezing from time to time when I download a large number of torrents simultaneously.
I wonder if an alternative Webtorrent implementation (not Webtorrent Desktop) in Rust on top of WASM might make those kinds of issues easier to avoid with its safeguards around concurrency and just generally making more efficient use of resources.
(Slightly edited repost from an earlier thread about Webtorrent, feels a lot more relevant on this one)