Just purchased a UHD monitor and I m having the same issue I have lasted update Big Sur macOS 11.6 (20G165), and no luck, de display is not recognized. I'm using a Belkin USB-C 6-in-1 Multiport. https://www.belkin.com/us/connect-usb-c-6-in-1-multiport-adapter/p/p-avc008/ I used to connect my mac to tv using the USB-C hub HDMI port. but now, on this version of mac, it's not working. Please, HELP apple!

My fix was to use Displayport, I bought a cheap USB-C to Displayport adapter and the monitor works fine. -> https://articulo.mercadolibre.com.ar/MLA-879587235-cable-adaptador-conversor-usb-tipo-c-a-displayport-hembra-_JM 👎 HDMI there is no way, does not work, I reinstalled to Catalina, also Big Sur and now I have Monterrey, no HDMI adapter or trick of refresh/ unplug works on my Macbook PRO 2019 with 4 USB-C ports. 👎 Thanks that my new monitor has the displayport input