6.602 will not update 6.703?
Also, in 6.703 and other recent iterations I can not seem to attach a file to an email but must 1st find the file then share with K9.
Update message,“App not installed as package appears to be invalid.”
Are you trying to update an installation from F-Droid with an APK from GitHub?
No, all installation files have been sourced from Github. I had an issue here before with updating where the newest version posted had a lower version number. I truly hope I don’t need to backup settings and blow out 6.703 to install 6.602? 
You do. Downgrading is not supported.