I successfully worked around the issue by updating the /Library/Application Support/Perceptive Automation/Indigo 2022.1/Plugins/MySensors.indigoPlugin/Contents/Server Plugin
/plugin.py script to recognize the internal 21 code.
Here's the diff:
34c134,135
< "GATEWAY_READY" : [14, "Gateway ready", ""]
"GATEWAY_READY" : [14, "Gateway ready", ""],
"DISCOVER_RESPONSE" : [21, "Discover response", ""]
715a717,719
elif itemType == self.getInternalNumber("DISCOVER_RESPONSE"):
# 21 Ignore
pass
P.S. Indigo 2022.1 is complaining about this plugin that it won't be supported in future releases. Is there anyone out there planning to update this plugin?