EDIT: ah just realized you are using the s905x4, in that case make sure you are loading these with CE NG and not CE NE
You can try manually loading the GoogleCoral modded BT drivers. These have limited functionality for me. LE devices aren’t detected, and pin authentication using BR/EDR doesn’t work.
But I can connect devices that use BR/EDR (legacy BT). Things like mice, keyboards might work if they aren’t LE
This is the driver from the first firmware that @vpeter compiled for MT7668 way above
https://filetransfer.io/data-package/Ko3U6Wdo#link
To load them, copy it to your USB stick, manually load it from ssh with
systemctl restart bluetooth
insmod bt_mt7668.ko
It would be good to get confirmation that you are seeing the same functionality as me. Maybe it will even work better for you?