It depends on which part of the polycule we're talking about
Vardah and Fabian love watching movies together when they have time, usually cheesy action schlock or comedies, or Vardah backseat games while Fabian plays
Vardah and Shizuki do a lot of craft projects together, some being practical things around the house like building furniture together out of scrap, like how their living room table is a modified copper wire spool or things like Shizuki's cosplays or reading together
Parah and Vardah argue about politics a lot but when they aren't doing that they enjoy cooking together
And Shizuki and Parah have fun with things like hitting up places like arcades or urban exploration points though for different reasons with Parah liking exploring free and open places while Shizuki likes haunted places
All together they probably enjoy a good movie or game night though with the former it probably takes a ton of time to decide on a genre.