Multiple notifications

I’m using K9 Version 5.806 and Android Version 10 in a Motorola MotoG Power phone. I’m getting multiple notifications for each new mail received, always 2 but sometimes 3 or 4 per new mail. I am using the K9 to receive my Gmails using only one K9 account. My wife has the same multiples on her Samsung Galaxy A41 using exactly the same set-up for K9 as mine.

I’ve seen some old discussions for earlier versions of K9 but I am not using the Arlo app which has been suggested as a possible cause.

I’m currently using push, but the multiple notifications started before I started push. All suggestions will be gratefully received.

Don’t sync Gmail’s “All mail” folder, or at least don’t let K-9 Mail generate notifications for messages in that folder.
When you receive a new message it will show up in the Inbox, but also in Gmail’s “All mail” folder. K-9 Mail doesn’t specifically support Gmail, it’s an IMAP client. So to K-9 Mail this new “Gmail message” looks like two new “email messages”, one in the Inbox and one in the “All mail” folder.