Very strange. It worked before. I am not shure if it disapeared when migrating from J3 to J4 or after. It did at least work in Ja Good J3, after changing from Ja Purity.
If I filled in the "captions" text in the id field in the second, "advanced", page of image editor, and marked class as "captions", the text apeared exactly as on intro image and full text image now. With the same css format.
As it is not working i Cassiopeia, I guess it is a J3 to J4 migration issue.
A caption feature on all the images in an article is necessary in a modern template, if you ask me.
Regards
Niklas