It looks like you have both Java 21 and Java 17 installed. But the active version is Java 17. You can switch the active version with update-alternatives. You should check the doc of this command. But out of memory: sudo update-alternatives --config java This should open a dialog box that let you choose between the versions that are installed on your system. More on reddit.com

There are reasons why the upgrade from 22.04 to 24.04 is not officially supported yet. Unless you have very specific reasons, it is always advisable to go with the official recommendations and wait till the first point release (in this case 24.04.1: release planned mid August) before upgrading from one LTS version to another. If the OS doesn't offer you the upgrade by itself, don't upgrade without need and without expecting problems. Ubuntu is actually rather easy and pretty stable if you follow a few simple rules of thumb: Always use a LTS version and don't upgrade before it's officially supported (That means: A pop up will suggest you the upgrade. You don't have to do anything but wait for that!), unless you have very good reasons to do something different. If you follow this rule, it's very probable that you will have a smooth and untroubled experience without major problems. If you use a non LTS version: Expect your experience to be a lot less stable. This is basically the testing field for LTS versions. Things can go wrong. Same goes for early upgrades of LTS versions. Expect any upgrade of a non LTS version or an early (i.e.: officially unsupported) upgrade of a LTS version to break your system completely and be prepared for that case. Edit: Addition to rule 3: Especially if you are not in the official LTS upgrade branch: Follow the developers' recommendation to check the release notes before upgrading,. That will not prevent all problems in all cases but it can make them less probable. More on reddit.com