1. Used different HDMI cables and different monitors;
2. Used different power supplies as well
3. Used different SD cards -- although not with the same image.
The thing is, with the Armbian Bionic downloaded image, the BPi boots -- as I stated, I did see its IP address and it responded to pings. Just no HDMI video.
Also, with all things equal, the old SD card still boots fine, with HDMI console.
I guess I'll try serial console when I get back to it.