According to CapFriendly, the Leafs have added 23-year-old Dylan Ferguson on a PTO. Ferguson has just 1 game of NHL experience under his belt (on an emergency basis for the Vegas Golden Knights), but he has also played 16 games for the AHL's Henderson Silver Knights and Chicago Wolves. Most of his pro experience, however, comes from the ECHL, where he played 27 regular season games for the Fort Wayne Comets. The Lantzville, BC native also racked up 13 games of playoff experience with the Comets in 2020-21.
There's no such thing as having too many goaltenders in your system, especially since it's likely the most injury-prone position. Plus, for the Leafs, who have yet to develop a bona-fide homegrown starter since Felix Potvin (you could also make a case for James Reimer), the more darts they have, the more likely one will eventually hit the dart board.
In 13 games with the Silver Knights last season, Ferguson amassed a 5-4-0 record (he was not the goaltender of record in 4 contests), to go along with a 2.90 GAA and a .907 SV%.