As part of me trying to get experience with mailcow i setup a local vm on my laptop with ubuntu 20.04 lts , restored a backup of a test mailcow and then after making a snapshot ( i know it’s test but also handy to hop back and forth for some testing) upgraded to 22.04 .. worked without a hitch.
Depending on the size of your cow, i find the mechanism for backup and restore or cold_standby so easy , that if you have some resources on a spare system you can always do a testrun and see what it does..