Possible os to install

hey, i am using a banana m4.
i want to use a different os than my currnet one, ubuntu 18.04.
i actually wanted to install a lighter linux distro, possibly lubuntu 20.04 or linux mint.
i am having problems installing it.
those are usually .iso files and not .img files
on wiki bananapi m4 these operating systems are not suggested and i could not find instructions to
install those.
did anyone here ever do it/knows how to?
basically how to install a .iso os on the bananapi?