... in version 72.0 and 72.0.1 just released. When examining Page View Info with respect to (dis)allowing images per website, the option no longer appears. Consequently all sites which I had set to block images (for purposes of download speed enhancement) have reverted to allowing same.
Any ideas?
I suppose I could go into Firefox's about:config and toggle that item globally, but I found it more useful to do such site by site (so that I wouldn't have be continually shifting back and forth between block/allow).

Has Firefox maybe ceded the functionality to an Add-on?

I suspect so, but normally Mozilla would announce such a dramatic change (and I see no evidence of the that ... the option just disappeared).
I thought I might add Image Block but I can't get it to behave on a per-site basis.

EDIT:
My installed uBlock Origin has a feature to "Block media elements larger than [selectable] KB" under Default Behavior. The trick to enable such on a per-site basis is to set the size (eg, 20 KB) in the size window and NOT to select item for universal default behavior. (It took a while to suss that out.)
It's not as good a solution as that which used to be incorporated in Firefox which simply removed all images, but it's something.

It turns out that Mozilla did announce the change in their release notes to version 72.0 (which I didn't scroll down enough to see).
They have, however, provided guidance to reversion to status quo ante:

Note that for now you can revert this change by setting this pref to true on the about:config page (no restart necessary).
extensions.contentblocker.enabled = true

We shall see.

I carried out the task but got some very bizarre behavior which seemed to be cured by restarting Firefox — contrary to Mozilla's parenthethical comment (see above).