Basically, the issue in this post still appears in Ardour 9 running on Catalina. The workaround there is still valid to start it from the terminal and then it asks, but it can take a user a while to find that particular post and figure out why Ardour is not recording.
It sounded like from the post that it was supposed to be fixed, I just want to report that it persists. Maybe you don’t fix because it’s an old operating system, fine, but reporting it FWIW in case it is an easy fix.
Did you check if Ardour is listed in
System Settings > Privacy and Security > Microphone
?
I do not think this is a bug. On my system, ardour asked properly
The thing with those apple questions is, once they are answered, the system will never ask again. So you need to go either into the settings and reenable it, or muck about with tccutil on the commandline, which is terribly undocumented.
Edit: A little further explanation of why the terminal workarround will ask again.
The Transparency Consent and Control (sounds Orwellian, right?) system asks for the permissions for the first process requiring them, inheriting from there.
So in the case of ardour, let’s suppose you clicked “Deny” at some point, the system remembers this for ardour.
But when you start it from the terminal, the terminal will start ardour and the system will check if the terminal is allowed to access the microphone. Either directly, or by using another app (ardour in this case). That’s why it will ask again, and even allow access, if ardour itself was denied before. But you allow this for TERMINAL! Not ardour. Just something to keep in mind.
Edit2: For linux admins, this is apples mandatory access control. Kinda like selinux or apparmor, if I understand correctly. Recent versions of macOS are immutable and have MAC enabled by default. (MAC on a mac, talking about confusing acronyms 
)
What @GenGen said.
Make sure Ardour9 is added/allowed here (and elsewhere):
FYI: I’m using even older macOS (Mojave), and all is good here! 
-J
Odd, It works here on macOS Tahoe (AppleSilicon) and BigSur (Intel). When the engine is started the first time for a given interface, a popup asking for permissions shows.
I believe it can happen if one accidentally disallows this once, but then re-downloading the .dmg (new file), and moving Ardour.app to /Applications again asks again.
Other than that one can manually configure this as @GhostsonAcid shows.
