I finally solved my frequent disconnects when sharing from my Oculus Quest 2 using Chromecast to Google Nest Hub Mini and Google Chromecast with Google TV by disabling the 2.4Ghz WiFi network on my router and keeping only the 5Ghz. Now both devices show up every time I want to cast and they don't disconnect ever anymore. It turns out that they used to be on the same network, but on different frequencies and Chromecast doesn't seem to like that at all.
Thank you I tried this and it also fixed my problems. I have a Nighthawk R7000 router, Chromecast Pro dongle and Sony 4k. The Oculus Quest 2 was disconnecting from Chromecast frequently until I turned off the 2.4G radio on the router.