Seriously? I configured all five of my email accounts on FairEmail literally a week ago, because K9 doesn't have a unified inbox. I was even going to pay for it, just so I could snooze mails without having to use the Gmail client.
I am surprised you are saying K9 does not have a unified inbox, because I use it daily (Settings/General Settings/Display/Show Unified Inbox). Do you mean that the way it works does not meet your needs?
> Do you mean that the way it works does not meet your needs?
Yes. I can't give you specifics, because even they are not clear in my head; I just know what FairEmail does out of the box works perfectly for me.
Also, filters. I don't move things out of my Inbox after having read them, so I rely heavily on FairEmail's powerful filtering mechanism. I can tell K9 to sort by unread first, but that isn't the same thing.
edit: Since we're on the topic, what alternatives are there? I know of none off the top of my head.
I hope to see updates to the app somewhere else.