after everything you already tested, this really does sound more like a firmware issue on the Suunto Race S after 2.39.20 than a router/network problem.
The interesting part is your router logs showing absolutely no connection attempt from the watch. That usually means the WiFi module itself is not initializing correctly after the update, not just failing authentication.
I d still try one last simple test: connect it to a very basic 2.4 GHz network without mesh/repeator features, WPA3, band steering, or hidden SSID. Some devices become weirdly picky after updates. But since you already tested multiple routers and hotspots, I honestly doubt your network is the real issue here.
Feels like the update broke WiFi handling for some units, especially since the problem started right after the firmware upgrade and before the maps could finish downloading.
