The easiest method I’ve found to embed an image so it shows up in the post here is to upload it to a site like Flickr and then copy the .jpg file. They have a way do do that and it includes the square brackets with the img but it is surrounded by other code that needs to be clipped. So a .jpg for sure or a .jpeg file might work too. Possibly.png may work. Various sites are different. That’s my experience but there may be other methods too.