“***I had a hard time seeing images with Firefox - not all the time, but enough of the time I had to open Chrome up to see images***”
Does Firefox have a “safe search” mode? It’s been years since I used it (Opera now and it has one).
If you have Safe Search and it’s on high, it will limit what pictures you can see.
I don’t use FireFox any more, just Brave, and it has many easy to adjust settings, I have on high as far as a lot of stuff like ads, but I can see almost any images.
I don't think that I have seen one, but my anti-virus provides that so I haven't really looked. My anti-virus has not obstructed images that I know of.