How do I install minecraft 1.7.10 and forge on a raspberry pi 3. Since I have this friend who wants me to install 1 mod to play on his server.
You should be able to just install it regularly, i.e. download forge from the site, run the jarfile with java -jar (forge-installation).jar
but keep in mind, to use 1.7 forge requires java 7 iirc.
edit: apparently only some builds of forge work, and you don't get sound. I found this information from https://html.dynu.net/index.php/how-to-setup-minecraft-on-raspberry-pi-forge-version-1-12-2/, but it should apply to 1.7 versions as well. Just experiment a bit (and maybe follow the url for the guide i listed, but with a different download).
another edit: apparently it doesn't work that way... try following the guide but using the download for 1.7 forge
You can find it in apt try
apt search minecraft
and you will find it. Then install it with the package name