Every time I join a channel, I have the correct count and correct “myLastRead” timestamp.
When I leave a channel, the count and timestamp get zeroed.
Is there a way to know if the channel has new messages even when I have not joined it?
If you leave the channel, then you lose all information about it… That’s the idea of being member of a channel.
If you need to provide this information to your connected users, you will have to use Platform API:
The response will include all user’s information about each of his channels.
You can’t from SDK since all you do from SDK will work for the connected user.