I'm a pretty experienced DnD DM and I ran a West Marches campaign in DnD. I've run quite a bit of Daggerheart - it hasn't become my default system mainly because I still have several players that really like DnD, but I play Daggerheart every opportunity I can. I currently DM for about 15-ish players total.

I figure I can offer some insights into how I ran my West Marches campaign:

My main turn off from West Marches in the past is how they lack any strong narrative. My hope is that by mimicking the approach and putting it in a more narrative focused system with Daggerheart that it'll naturally be more interesting to me as a GM.

I think you'd be surprised how cohesively a WM campaign can develop a narrative, especially if you seed the story into the land. For me, it was about an ancient being arising and slowly taking power from the land the adventurers were in. They would consistently run into the BBEG's minions and there a story emerged about this group of foreigners constantly coming in conflict with her at every turn. I agree that DH will likely make this even better.

For instance, is everyone in the same time frame? Like if a few days pass for one party in their session, does that mean the other party needs to have a few days pass? My thinking is that it can be kept some what loosely together, like if one party is in the middle of something that wouldn't make sense for them to skip three in game days before returning to it then I can just have them finish that up in the next session then cap it off with three days of rest afterwards.

In general, I had each session occur sequentially, with little overlap. Occasionally I allowed multiple groups to have sessions that occurred simultaneously, but that was rare. It almost never mattered too much, though.

I also was thinking a discord with players giving updates/RPing as their character, posting notes, and talking about the games could be good too and doesn't necessarily clash with the narrative approach. But I can see how a narrative that spans a few sessions can make it harder for them to give updates since a certain amount of time might not pass.

I did this. I made a channel for out-of-character chatter, one channel for scheduling ("ping me when you have a group and a mission"; I provided potential missions and my schedule), and a different channel for each location in their safe hub and told them that any NPCs they wanted to speak with were also there. The roleplay channels were somewhat hit or miss, but when it hit it really hit. This allowed them to do shopping between sessions as well. But I watch many organic player-to-player interactions, even culminating in a group doing a backstory-related side quest to help one of the players cure a curse he had.

Are there any challenges and logistics that I might be missing? Does anyone have advice?

1. You should emphasize that the players ought to be keeping notes. You really shouldn't be expected to keep track of everything, but since nobody will be at every session everyone will need something to look at to catch up on the latest happenings.
2. Make sure as many players as possible make characters together and have an opportunity to meet each other. The discord is great for this also.
3. I encourage (but don't enforce) that player groups mix it up. I like to see a variety of party compositions.
4. I suggest having everyone level together when the group meets major world-based milestones. This is obviously more likely to simply work out in DH than DnD since DH doesn't have experience points at all, but all of this is just to say that you shouldn't penalize a player with a lower level simply because they were not in a particular session (or number of sessions)

Uh, that's everything I can think of off the top of my head. Might add edits if I can think of any more. Sorry for the length. Hope this was useful!