I have been using an old phone and K-9 Mail 5.6 for years because I need to be notified of incoming emails to a specific folder as soon as possible. K-9 works beautifully with poll frequency set to 1 minute.
Recently I bought a Samsung A53 running Android 11, but it looks like the minimum poll frequency is greater than 1 minute for recent versions of K-9 Mail.
So my question is this: what is the last version of K-9 that allows 1 minute poll frequency, and what is the latest version of Android that it works on? If necessary, I will return the Samsung phone and buy a phone that will enable me to use K-9 Mail at 1 minute poll frequency.