I hope this will help you all sort it out: https://www.reddit.com/r/bootcamp/comments/h9skhy/bootcamp_windows_10_2004_bluetooth_fix/
In my case I needed to update the Broadcom Serial Bus Driver over UART Bus Enumerator from 12.0.1.873 to 12.0.1.874
TLDR: I've tried many solutions before I came to this driver version and finally I have my keyboard (which is an Apple BT Magic Keyboard) and mouse (which is an MX Master S2 from Logitech) working on my Windows (which is running in bootcamp on my MBP 2017 and will probably install on my MBP 2020 as well since I found this fix for BT).
Since the update to Win 10 2004 I constantly tried to fix the BT but w/o success and I was so frustrated looking at the hardware I cannot use... :-/
Hey Microsoft, please, next time when you release an update, test it thoroughly!
Since I'm a software test engineer myself, I know what I'm saying :)