Yeah DMs are a pain on relays. Same for notifications. Without a database it’s hard to keep track of what was seen and what wasn’t. You can use local database but it seems to not always work well.
Discussion
Yeah I run Citrine on mobile and it doesn't seem to help with that issue. Bit I also don't know what kind of events it even supports as I forgot about it until you mentioned local relays. I hide or turn off a LOT of notifications.