Instances are broken

My Minecraft Launcher was working fine three months ago. Recently, I have been having an issue where the instances tab is completely broken. I can still play instances without trouble. However, half the time, the dropdown menu next to the Play button won't work. I have also attempted to create new instances, but it doesn't let me select a version older or newer than 1.18.2 (the latest version). I put the April Fools' Minecraft 2.0 into the launcher, for example, but when I click on it when creating a new instance, Minecraft 1.18.2 is still selected. The launcher also won't let me delete an old instance of 1.0. This is a huge problem for me, as I enjoy exploring older versions of the game.

For a bit more information: I also tried to reinstall the launcher - I removed it, and then downloaded the "Minecraft.deb" file again. It failed to show results.