It's been a year since the last reply, but just to add -- there's also a hardware way of doing this. There are small devices which plug into a HDMI-port and emulate a monitor.
If you use such a device on a Pi, the Pi will think there's an actual monitor connected.
The ones I've seen are normal sized HDMI connectors, but I'm sure there will be micro-HDMI ones ...
The Pi should automatically connect to the monitor without having to change anything.
Are you connecting to the correct HDMI port on the Pi? It's the one closest to the power jack.
Do you know that the connecting cable is good? Can you connect to the Pi using SSH?
The answer is to add
To your /boot/config.txt along with the above hdmi_mode, hdmi_group, and hdmi_drive options
This should really be mentioned as a necessary option. Currently the docs only say that it will output HDMI even if no HDMI is detected, which is confusing at first because HDMI is showing.
In fairness, tvservice does say ...
I have the same problem.
But I do have a sound icom on my 4b 8gb running Buster OS.
I ran across a post (don't remember where) with a terminal command to reset your panel toobar.
I found it under help for, "Deleted Toolbar Panel help" .
It restored the sound icon, for me.
My fix for the "No Sound issue", is crude & won't help U ...