Hello everyone! Seems like quite a few of you have encountered this issue by now. We’re sorry for the inconvenience this may have caused! Meanwhile, I do have some good news for you all.
A new version of Simlink is now released! 
It is temporarily available here. This new version is compatible with macOS Big Sur and should be able to run without any issues. It will soon be included in all new installations of the Charts application, and users running older (working) versions of Simlink are already being prompted to update to the new version.
See you in the skies!
Regards,
Malte