I’ve had the same problem for a week or so (Pixel 9a, Android 16) and have found that changing the Companion app setting under Home network (Your home SSID) at the bottom of the screen is an option “When loading dashboard and unknown if connected to home network” select the option “Use internal connection URL” instead of “Use Home Assistant URL (recommended)”.
Changing this has made my dashboard open reliably fast when I’m home and hasn’t impacted my remote use.
YMMV, but it helped me.