Firmware 5.70 worked fine with my bluetooth headphones (outdoors/left wrist). There was the occasional dropout but nothing unmanageable.
Firmware 5.90 is a different story entirely. So many dropouts that my headphones (QCY QS2) are basically unusable with the watch outdoors.
It's all well and good to force upgrades if you're sure your software is up to the job. But too often, new firmware breaks things on this watch.
I seriously think Garmin needs to improve not only its software development and quality control (see: https://www.dcrainmaker.com/2019/06/competitor-software-instability.html), but also its customer support. I don't even bother contacting customer support after a few instances where they couldn't understand even the most basic operations of the watch.
And while I'm complaining: how is it that the list of compatible bluetooth headphones hasn't been updated in years and has the same tired 9 headphones on it?