I noticed that there is not easy list of OSes that will run on the RPi4 so I made one I will add links to every OS available for the RPi4 here as I come across them
The minimum sd size for any OS to boot is 8gb, if you put something like Lakka (500mb) on a 4gb card the pi4 will not boot it
Lakka, works well at stock speeds, minimum sd size is 8gb
Ubuntu Server, works well at stock speeds, overclock if you want acceptable performance in a desktop environment, minimum sd size is 8gb
Manjaro, have not tested, minimum sd size is 8gb
LineageOS 16, works well at stock speeds, overclock reccomended, minimum sd size is 8gb
Raspbian, works well at stock speeds, plays minecraft at acceptable speeds but is 32bit, minimum sd size is 8gb
Endless OS, have not tested, minimum sd size is 16gb
Gentoo, have not tested, minimum sd size is 8gb but not reccomended
LibreElec, have not tested, minimum sd size is 8gb
DietPi, have not tested, minimum sd size is 8gb