Masonry knee wall possibly load-bearing?

No, I hadn't. I wouldn't know how. Otherwise, I would never have had to ask the question here.

If you show image material from the "back side," it may be possible to say more about it. Existing building forensics is less complicated than many laypeople think.

No problem. I can’t imagine that anyone gains much insight from this. If they do, I take my hat off.

From the overall view, you could therefore see that the knee wall does not support a purlin (which would also be very unusual). This allows its load-bearing function to be excluded, but it can still fulfill a stiffening function (which it can also perform intermittently).