@hooeef I have used the SD card from my RaspberryPI4 with Manjaro OS installed, in a RaspberryPI3B+, it works albeit a bit underwhelming, I think it is possible to do a minimal install to save space. You may need to install java see:-
https://linuxconfig.org/how-to-install-java-on-manjaro-linux currently OpenJDK14 is default (which is fine).
I replace java folder (of processing install) with a symbolic link to the distro installed java to use (just link /usr/lib/jvm/default-runtime , read up on how to create a soft link on unix/linux). PS once you get used to it you may come to love Manjaro which uses Archlinux package management system rather than Debian package management (RaspberryPI OS). The 64 bit RaspberryPI OS is coming, but like a release version of Processing-4.0 it will be a longtime coming.
I am writing this addendum on my RaspberryPI3B+ using said Manjaro install (and the startup time for the processing ide is dreadful if you could avoid using ide on RaspberryPI3B+ you might get better results the ide is a resource hog).
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