Appium is automation test framework to test mobile website and mobile application, including Android. To be able to use Appium, you need to run Appium-Server. You run Appium-Server inside docker-android container by opening port 4723 and passing an environment variable APPIUM=true.
docker run -d -p 6080:6080 -p 4723:4723 -e EMULATOR_DEVICE="Samsung Galaxy S10" -e WEB_VNC=true -e APPIUM=true --device /dev/kvm --name android-container budtmo/docker-android:emulator_11.0
The user can pass the additional parameter to Appium Server through environment variable APPIUM_ADDITIONAL_ARGS. Please check this page for possible arguments that can be passed to Appium 2.x.
The user can connect docker-android that contains Appium 2.x to Selenium Grid 4.x without any additional configurations / changes in docker-android project. Please check this page for detail information