Retevis RT73 Configuration and Firmware at the time this was written..
|Version Date||Nov 27 2020|
As you can see from the image above, there is built in broadcast FM radio reception. Some of the Retevis RT73 ads do mention the FM radio, but provide no details or even mention in the specifications ( Retevis.com_RT73_specs).
There is no sign of this capability in the CPS software or what could be nice feature in an ability to program one of the keys to go directly into broadcast FM reception mode. Anyway, you can bet to the above FM screen from the menu and selecting Appendix the FM menu is one of the sub-menus available.
Note: Radioddity has released the Radioddity DB25-D which appears to be exactly the same radio as the RT73 just with different branding (Radioddity instead of Retevis).