Prior to about 7-14 day ago, ‘page source’ was a menu item when right clicking on the image and quickly (just a few seconds) locate/copy the HTML for the image.
MS changed something.
Okay, that's interesting. I don't think I've ever seen or used the option as you describe it. I -have- used "Copy Image Location" which gets the URL of the image, but not the HTML code of the <IMG SRC=...> reference.
Well, you've piqued my interest. :-) I run Win10 in a VM, and I keep old backup copies of the VM in case of damage, malware, or a screwed Windows Update. The backups pre-date the change you mention (more than 2 weeks old) by a good bit.
I'll see if I can confirm/deny the presence of such a context menu option in the old versions.