I got the FTB-launcher successfully installed on my Ubuntu 22.04 LTS.
sudo apt update
sudo apt install openjdk-17-jre
INSTALL4J_JAVA_HOME_OVERRIDE="/usr/lib/jvm/java-1.17.0-openjdk-amd64" sh FTBA_unix_202206081143-2e021f8e74-release.sh
Hope this helps!