Malwarebytes incompatible with OS 1015.5?

MalwareBytes is aware of it, and are already working on a version that will work in macOS 10.16.

https://support.malwarebytes.com/hc/en-us/articles/360045251654-Legacy-System-Extension-warning-on-Malwarebytes-for-Mac-devices

That's a general warning the OS is giving to all users who have any kind of third party kernel extension installed.

The next major release of macOS will not allow third party kernel extensions. It's just warning that any third party software you're using that installs such extensions will not work in 10.16.

All vendors who now user kernel extensions will have to use a different method to load items at startup.

https://support.apple.com/en-us/HT210999

The message should have mentioned the name of the vendor the extension is from. But in short, all third party extensions are in the following location, along with ten default extensions installed with the OS.

/Library/Extensions

For now, you don't need to do anything.

Have you contacted Malwarebytes support for Mac? You may need to submit a trouble ticket with them to receive guidance on this looming, future, kernel extension issue. Also, have you checked for updates per the application menu, in case you are still using an outdated version?

I use the paid version, 4.4.11, in Scanner only mode (no real time protection) and it gives me the warning (each time that the MacOS is updated).

Edited to add: Up-to-date, according to Malwarebytes -> Check for Updates

I use the free version 4.4.11 under 10.15.5 and it does not give me warnings

You're welcome. 🙂