graphic: 0.865
device: 0.840
semantic: 0.683
mistranslation: 0.656
performance: 0.651
boot: 0.644
user-level: 0.619
assembly: 0.543
VMM: 0.516
vnc: 0.486
kernel: 0.485
PID: 0.468
ppc: 0.448
socket: 0.442
risc-v: 0.440
permissions: 0.438
register: 0.430
architecture: 0.412
debug: 0.370
network: 0.370
files: 0.350
TCG: 0.296
virtual: 0.287
arm: 0.271
hypervisor: 0.136
peripherals: 0.133
i386: 0.106
x86: 0.103
KVM: 0.082

Converting qcow2 to vmdk on MacOSX results in a non-bootable image

When using qemu-img convert -O vmdk  with version 3.1.0 or 4.0.0 on OSX (10.14.3) with a qcow2 image  (https://cloud-images.ubuntu.com/bionic/20190703/bionic-server-cloudimg-amd64.img), the resulting image is not bootable.

Running the same command on Ubuntu 18.04 results in a bootable image as expected

Try the solutions in 1828508 ( -o  adapter_type=lsilogic,subformat=monolithicFlat)  1776920 ( -S 0 ) do not work either

What other steps can I take to troubleshoot?

Does the problem happen only when the image is on APFS? when the destination is on APFS? Neither? Try to see if it's the filesystem. Use OSX to convert images on a non-APFS formatted external drive to see if that improves your luck.

I'm assuming this is a duplicate of 1776920 which is still open because we have no OSX developers willing or able to debug this problem.