I had the same issues with bluetooth not working messages several times yesterday when trying e and also lineageOS.
Not sure exactly how I fixed it each time, but I just had to re-install the same firmware again - doing a wipe of system again, and format data, clear cache etc.
For some reason twrp gives a /firmware access error, but then booting into the rom again, after the second install fixed the bluetooth nagging me and all worked again.
EDIT: Just had a thought, could this be related to the A/B partitions ?
EDIT 2: It is - see this post to fix: