Check the device settings for the RM4 Pro in the Broadlink app. You might see a switch that “locks” the device so that it can’t be seen on the LAN. Unlock it, and all should be well.
I have installed the patch-23 and rebooted (again this morning) and I am still unable to add my Broadlink RM4 Pro.
Logger: homeassistant.components.broadlink.config_flow
Source: components/broadlink/config_flow.py:48
Integration: Broadlink (documentation, issues)
First occurred: 7:17:29 AM (1 occurrences)
Last logged: 7:17:29 AM
Unsupported device: 0x653c. If it worked before, please open an issue at https://github.com/home-assistant/core/issues
2021-01-31 16:00:52 ERROR (MainThread) [homeassistant.components.broadlink.config_flow] Unsupported device: 0x653c. If it worked before, please open an issue at https://github.com/home-assistant/core/issues