TLDR: Flickr may not support partial equirectangular images, but Google Photos does.
If the image was a full 2:1 equirectangular image:
-out test1.jpg \
However, the image you linked to is not 2:1, not even close.
Let's assume it can be treated as a cropped 2:1. If it wasn't cropped, the height would be half of the width:
22902/2 = 11451
... So we'll set
Next we need to calculate
CroppedAreaTopPixels. Again, we divide the width by 2 to get the "full height", then we subtract the actual height to figure out how much is "missing". Next, we'll divide this by 2 to find the amount missing "above":
((22902/2)-1061)/2 = 5195
... So we'll set
5195. Note that this assumes the panorama is more-or-less lined up with the "true horizon". If you had captured more sky than ground, you would want to use a smaller number here, which absent more information to go on, would need to be figured out by trial-and-error.
Plugging these two numbers into the basic command above yields:
-out test2.jpg \
Tested in Google Photos, looks good, no noticeable issues.
Tested in Flickr: no good, doesn't use panorama viewer.
I then took one of my own 2:1 equirectangular images, and uploaded it to Flickr, and the panorama viewer was used, but bleh, Flickr does a poor job of stitching the very bottom of the image (nadir, looking directly down) [ref], Google Photos looks much better.
Next, I cropped my 4096x2048 image using ImageMagick:
convert in2.jpg -shave 0x512 test4.jpg
... resulting in a 4096x1024 image with 512px missing from the top and bottom.
Next, I updated the EXIF data as follows:
-out test5.jpg \
Finally, I uploaded it to the two services I tested on:
Google Photos: looks great, just like the original but with a circle missing at the top and bottom of the sphere (a spherical segment, missing two spherical caps).
Flickr: not showing panorama viewer.
... Which leads me to assume that Flickr may not support partial equirectangular images.