qBittorrent won’t attempt to find any I2P peers unless you add I2P trackers to the torrents. After that it’s hit or miss similar to public torrents.

These are working public trackers in I2P that I know of:

http://w7tpbzncbcocrqtwwm3nezhnnsw4ozadvi2hmvzdhrqzfxfum7wa.b32.i2p/a

http://opentracker.skank.i2p/a

http://opentracker.r4sas.i2p/a

http://opentracker.dg2.i2p/a

This tracker is also in I2P but it only tracks torrents registered at their site:

http://tracker2.postman.i2p/announce.php