I've been playing around with a 64bit arm .img install for RaspberryPi. You've always been able to install sark on the 64 bit Pi 4 but, to make it easier, we've put up a ready-to-run image here:-
http://www.sailpbx.com/sail/raspi-arm-64-img/
Download it and burn it onto a microSD card with the RaspberryPi imager and it should just run on any Pi 4.
N.B. The image inflates to about 7.6Gb so you'll need a micro SDcard of at least 8Gb.
SSH login creds are
UID sark
PWD sarkadmin
The front-end browser is just the same as always.
UID admin
PWD sarkadmin