Thank you. I shall study PartitionedCall and StatefulPartitionedCall and how they can be used to make a loop. Actually I have not yet found a C++ description for that and did not get much smarter from the Python description either, but will make some more efforts.
Nonetheless, your reply made me maybe even more confused:

I had watched the attached Skye’s video few times earlier (and asked the same question there as a comment), but there she also talks about tf.while_loop being broken down to these 5 elementary operations (see chart at 2:20), but does not even mention PartitionedCall. The details at 9:53 also show the classic set-up.
Maybe you do not delete deprecated ops, but at least they are marked as such in the ops.pbtxt (e.g. AdjustContrast). These five ops are not marked as deprecated, so I would assume that they are still to be used.
Even if these 5 were a mistake and now there are better ways, I still wonder how these were supposed to work, when an ops cannot be created without its input, but its input is to be declared later.