Using Processing 3.x with JDK and/or compiler source 14 is unlikely to work anyway. Anything above 8 is likely to give you issues.
I have a Java 11+ fork of Processing 3.5.3 at https://search.maven.org/search?q=g:org.praxislive.libp5x but it needs a bit of work to use with anything other than LWJGL renderer. More for internal use at the moment, but I intend to tidy up and support other use as soon as I get some time to work on it.