Before I upgrade my Mac’s OS to Sierra I wanted to first check in to see if it’s compatible with Audacity please? last time I downloaded El Capitan, I couldn’t use Audacity until a few upgrades later, which was terrible for my business!!
I meant, what the problems were that you encountered in Audacity until later El Capitan. For example, USB audio was problematic in early El Capitan, but that did not only affect Audacity.
Audacity 2.1.2 is not flawless on any version of macOS. A lot of bugs were fixed in 2.1.2 but new ones came in because we had to update to a later version of the toolkit that provides our user interface.