
Geometry nodes, for example changed a lot from 2.93 to 3.0 and many geometry node setups simply won't work. There are known issues with this update, since it is the first major release of Blender in 21 years. Note that Blender makes a strong effort to be backward compatible: Blend files from earlier versions are likely to be useable with later versions, so you should mostly be able to read your 2.93 files with 3.0 Blender.

Because Python compatibility was broken in 3.0 this will be true for many add-ons. Blenderkit, for example has different versions for 2.9 and earlier than for 3.0. Be sure to check the add-on's site and download the version for 3.0. One downside of this is that if you install 3.0 you'll also have to reinstall any add-ons that you've downloaded and installed. to represent, for Linux, MacOS, and Windows. You can find out more at Blender's Directory Layout which describes in more details, including the paths that I used. This includes both Blender's own files and any Add-Ons. and your 3.0 version will install in directories like.

Any time you do a standard install of a blender version N.MM.x it is installed in various directories that have N.MM in their paths, so your 2.93 version will install its files in directories like. Blender is specifically designed to keep its versions separate from each other.
