JDownloader runs perfectly fine on BigSur with AppleSilicon, just tested yesterday

Extraction support will follow shortly with upcomming JDownloader updates.
At the moment only manual installation will work.
Installer will follow as soon as BigSur/AppleSilicon is supported by the software we use to create installer.
1.) Download supported Java. eg from Zulu
azul.com/downloads/zulu-community/?architecture=arm-64-bit&package=jdk
2.) Create folder for JDownloader, eg in your user home and download JDownloader.jar into it
https://jdownloader.org/jdownloader2 , see Other
3.) Start JDownloader.jar
At the moment the Java package from Zulu is zip only, means you have to manually start JDownloader.jar via /path/bin/java -jar JDownloader.jar. Once full installer dmg package is available, you should be able to normal double click JDownloader.jar