I set up my RPi 4 with a 64-bit kernel and an SSD root drive thanks to these instructions: https://www.jeffgeerling.com/blog/2020/im-booting-my-raspberry-pi-4-usb-ssd
After installing OpenJDK 11, and replacing the included x86-64 JDK with the arm64 version, as mentioned in previous posts, I was able to use the Processing4 build (2020-04-26_22-59-00_linux_aarch64.zip) successfully 
Tried out some simple sketches of mine and they ran perfectly. Awesome work!