Starting in macOS Catalina 10.15.4, Apple has started to warn users about software on their devices that is using legacy extensions.
In 2019, Apple announced that kernel extensions (kexts) would be deprecated in a future version of macOS and began to provide an alternative mechanism for kexts called "system extensions." This is likely to occur in macOS 10.16. This warning is outside of Fleetsmith's control and can only be fixed by the developer of the specific software that is listed in the warning.
This warning will not stop the software from functioning or prevent users from using the software at this time––it is simply an informative warning. Most software developers have begun planning and implementing the use of the new system extensions, however you should contact the software developer listed in the warning to ensure they are planning for the update. Without moving to a system extension it is likely their software will lose functionality.
You can read more about this notification and System Extensions directly from Apple here: https://support.apple.com/en-us/HT210999