About a year ago, I was playing in a "West Marches" style campaign on Roll20. All the in-between adventure stuff was handled on a Dischord server. I think there were 3 DMs and about 20 players at any given point.
One clever thing they did was add an "Adventure Journal" text channel to the Dischord server. If you posted an in-character journal entry, one of the DMs might give you a small amount of xp. You could also get a little xp if you kept a map. Mind you, this was a very small amount of xp, never enough to level your character. But it made everyone write journal entries and put some effort into it.