In order to run Ghidra you need to install the Java Runtime Environment
First Update
sudo apt update
Next install the OpenJDK:
sudo apt install default-jre
Verify that you have install java
java -version
Next Install OpenJDK 11 JDK and the OpenJDK 11 JRE
sudo apt install openjdk-11-jdk sudo apt install openjdk-11-jre
Now Navigate to https://ghidra-sre.org/ and click the Download.
Once you have downloaded Ghidra it should be in your downloads folder unless you changed it to another folder. Then go into that folder and extract it.
sudo unzip ghidra_9.1.2_PUBLIC_20200212.zip
Once you have unzipped the folder go ahead and go into that folder:
cd ghidra_9.1.2_PUBLIC
Then run the executable:
./ghirdaRun