Turns out there’s a newer driver version than in that Reddit post. Try the following:
wget https://dlcdnets.asus.com/pub/ASUS/wireless/USB-BT500/20200909_LINUX_BT_DRIVER_KERNEL_5.7_COEX_v0202.zip
bsdtar -xzf 20200909_LINUX_BT_DRIVER_KERNEL_5.7_COEX_v0202.zip
cd 20200806_LINUX_BT_DRIVER_RTL8761B_COEX_v0202
sudo make install INTERFACE=usb