Ok, so I've "won" twice now (finished with >2500 renown - Adventure mode + Classic difficulty), but my scores aren't showing up in the leaderboard. The leaderboard remains completely empty regardless of what filter settings I pick.

When I first started the game, it asked me something about submitting scores to the leaderboard... At the time I picked no as it said I could toggle this at any later time in the options. However, I've carefully combed through the options and I can't find anything related to this.

Has anyone else seen this? Does the leaderboard work for anyone else?

Answering my own question here, the setting is stored in:

$installdir/game/userdata/Renowned Explorers International Society/savedata/metagame.1

You'll want a hex editor to edit it, I used Okteta. Search for DisableLeaderboards and edit the 8 bytes immediately *before* this string. Assuming you're going from disabled to enabled leaderboards you should make the following single bit edit:

00 62 01 6B 13 00 00 00 -> 00 62 00 6B 13 00 00 00

Save the file and you're done. You should have working leaderboards now.