GTK3 is 3rd party software. Apple doesn't support it in any way. It is the responsibility of 3rd party developers to ensure their software runs on the latest Apple operating systems.
It is always possible that there is a bug in the operating system itself. However, if a problem like this only occurs in one very specific set of apps, then that probably isn't the case.
I tried to track down what this problem is. It sounds like there are multiple issues. I did find one issue that is related to mouse tracking problems. If the description of the problem is correct, then this is a bug in Ventura. Unfortunately, it is a bug that is very unlikely to be fixed. This is code that Apple "soft deprecated" 15 years ago.
If you depend on this software, and running it under Ventura, then you have a few options:
1) Wait for Apple to fix the bug in Ventura
2) Wait for the developers of GTK3 to fix it
3) Take some action on your own
I recommend option #3. As I said above, Apple isn't going to fix this bug. I don't know if Apple even knows about it. You can file a bug report with Apple to make sure that Apple does know about it. I think you'll need a free developer account to do this. Don't assume that anyone else has already done this. One of the things that Apple uses to decide which bugs to fix is how many duplicate bug reports they get on the same issue. So the more reports, the better.
But again, don't get your hopes up. This is something that Apple re-wrote 15 years ago. Even if there was a bug in the new version, Apple probably still wouldn't fix it. Pretty much all Apple development on macOS these days is devoted to porting iOS code.
An even better option would be to take some action on the open source side. As I said, I did manage to track down that one bug report. From the looks of the kinds of patches they are working on, they don't seem to be on the right track. Create an account there and tell them that they shouldn't use the "addTrackingRect:owner:userData:assumeInside:" method. They should switch to tracking areas instead. That's your best bet.
