No. Do not massage the skin near or on the ulcer. This can cause more damage.
Near or on. That covers the skin around the sore, not just the sore itself. This is the part that catches people out, because rubbing around the edges feels like the careful version of the same idea.
The belief behind the question is an old and reasonable-sounding one: that rubbing improves circulation to an area that’s short of it. But the answer doesn’t change. Massage near or on the ulcer can cause more damage.
It belongs with the other things that cause harm through friction. Avoid further injury or friction by not slipping or sliding as you move positions, and by trying to avoid positions that put pressure on your sore.
What is recommended for the skin is gentler and different in kind: care for healthy skin by keeping it clean and moisturized. Moisturizing means applying, not rubbing.
If improving circulation is the goal, there’s something else for that. Ask your provider if it’s OK to do gentle stretches or light exercises, which can help improve circulation. That’s a question for the provider rather than something to start on your own.
One related instruction for anyone using powder for friction: lightly dusting the bedsheet with medicated talc powder is acceptable only if the pressure sore is not an open wound.