So if they're going to make mounts useable in dungeons:

[Enla]

The mount-in-dungeon thing appears to be a separate instanced thing, not actually running around in your Expert Roulette dungeon with a mount. It seems to be under an "Explorer" mode version of that dungeon, which lets you use limit breaks and mounts freely. At least that's what I understood from the translations.

Honestly I'm kinda excited they're doing this from an RP perspective if that's the case. I've really wanted to RP in some dungeon locations (unsync'd and with consenting people mind you, not forcing myself on a random duty group) but the kick timer just doesn't make it worth it if you prefer to do any long form writing.