Is Torchlight 2 cross-platform coop possible ? (Switch + PC)
I believe the answer is no.
(I also played TL 1&2. 1 was clearly single, 2 had LAN/IP possibility for PC, but cross-platform is a huge endeavour to take. If there would be a chance, that could be visible on hosting a game, showing up several different console network integration, and game discovery - and I don't see such in there. Modding is still a possibility, but I think vanilla game is clearly out of this.)
Forgive me to link another Reddit, it is 4 days old by today: https://www.reddit.com/r/Torchlight/comments/iv5mds/torchlight_2_pc_and_switch/