Raspberry Pi 5 - HDMI Woes & Solution

TL;DR

Problem: New Raspberry Pi 5 boots, but no HDMI

Solution: Add "video=HDMI-A-1:1920x1080M@60D" to your /boot/cmdline.txt

How to get it done

Boot your device and SSH to it.  

If you can't SSH, follow instructions here

Once logged in:
Become root

sudo su -

Change to the boot directory

cd /boot

Edit the cmdline.txt file.  (vi is always there, but use whatever editor you like)

vi cmdline.txt

Add 

video=HDMI-A-1:1920x1080M@60D 

to the beginning of your /boot/cmdline.txt file.  

cmdline.txt is a (long) single line file, so DON'T HIT RETURN.

Save the file. (:wq in vi)

Reboot your device

reboot

Done!

Note: 1920x1080M@60D is a pretty standard setting for most monitors.  

If it doesn't work for you, you may need to adjust.

There are lots of details here, which is how I got this far.