GNU/Linux MX Installing Rtl8761B Bluetooth Driver Guide
The tutorial shows you step-by-step How to Download and Install Realtek Rtl8761B Bluetooth 5.0 Driver in MX GNU/Linux desktop – Step by step Tutorial.
And Rtl8761B Bluetooth Driver in MX should be present on Kernel, what may be missing is only the Firmware.

1. Terminal Getting-Started
How to QuickStart with Command Line on MX GNU/Linux:
In case, to get more insight about the Bluetooth Issue run:
sudo dmesg | grep Bluetooth
And in case of a missing Firmware in output you find something like:
Contents