I recently modernized a project and switched from JDK 8 to 17. Although I'm not sure if this is really the root cause, as I didn't use Hot Swap for quite a while.
Now, I'm getting
Hot Swap failed
Tomcat: changes to class attribute not implemented
Tomcat: Operation not supported by VM
for even the tiniest change in the source code, e.g. changing a condition in a return statement from logical or || to logical and &&.
If I change the code back and rebuild again (just for the sake of the experiment), it says All classes are up to date. Nothing to reload. This means that the connection to the JVM seems to work, and also the check for changes in the classes.