I had problems installing the new RPi3-addons via GUI (error was something like "wrong addon structure"). So I installed the RPi4/RPi5-addon virtual.rpi-legacy-tools and just replaced the file _GPIO.so in folder /storage/.kodi/addons/virtual.rpi-legacy-tools/lib/RPi with the one from your new ZIP-file. Now rpi-gpio works on my 3B-device.
LuRu, thank you very much for the quick help.