I have upgraded my MAcBook to MacOS Big Sur and have found significant issues when using Servoy Developer.
The issues are almost all related to screen refresh problems and have been reported to the main Eclipse BugZilla site. Until these are resolved (and the corresponding fixes brought into Servoy Developer) I would not recommend the upgrade. It is particularly difficult to debug in developer as the code shown in the window can be a mixture of multiple files if you jump from one source file to another (or even jump around within a file from one method to another) during debugging.