After some one-in-the-morning experimentation, I believe the issue with imgur’s image hosting to be due to the URL, as before the issue (check any post that at one point had a working image) the url was https://I.imgur.com/generic, however for whatever reason the imgur team decided to change it to http://imgur.com/generic.
For example, using a picture of a kangaroo taken in Mulligans Flat nature reserve,
If the format  is used, the result is
However, if the url is changed to  then the result is
Note: this is done on a iPad using Firefox and Safari
I figured that out this morning. I tried to go to the edit page, then open the link and
Tada
The picture is now present
Both the s at the end of https and the I. in the i.imgur.com have to be removed @Oski
Oh, and now both work XD
Yup, that's it. To make pics work we have to remove one simple S letter from the link and the images work. But why did they decide to make their site unsafe? (https sites are safier that http sites)