Okay, so...
I reread the Godot Docs about the android export. Turns out, it asks for Java 8, not 11. So I tried to install JAVA version 8 as well as other stuff, like JAVA_HOME, PATH, and /etc/environment.
MyName@pop-os:~$ java -version
openjdk version "1.8.0_282"
OpenJDK Runtime Environment (build 1.8.0_282-8u282-b08-0ubuntu1~20.04-b08)
OpenJDK 64-Bit Server VM (build 25.282-b08, mixed mode)
sudo gedit /etc/environment
PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin"
JAVA_HOME="/usr/lib/jvm/java-8-openjdk-amd64/bin/"
source /etc/environment
MyName@pop-os:~$ echo $JAVA_HOME
/usr/lib/jvm/java-8-openjdk-amd64/bin/
MyName@pop-os:~$ echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
MyName@pop-os:~$ which java
/usr/bin/java
But...
ERROR: JAVA_HOME is set to an invalid directory: /usr/lib/jvm/java-8-openjdk-amd64/bin/
Please set the JAVA_HOME variable in your environment to match the
location of your Java installation.
Exit Code: 1
Addendum:
I'm not sure if this is related, but I'm gonna add Export Editor Settings:
Adb: /app/bin/adb
Jarsigner: /app/bin/jarsigner
Debug Keystore: /home/myname/.android/debug.keystore
Custom Build SDK Path: /home/myname/Android/Sdk