Yeah, @harvey44 sometimes I'm not even sure I had an orgasm! Mainly I find out that the anticipation phase has passed and does not return, so whatever I had, that was it. Sometimes it's better than others, but it is never like before PC. Over the last 2+ years I've coached myself to accept whatever is, try whatever helps, and enjoy who I am. One thing is for sure, I don't have any trouble with premature ejaculation :-).
Now, what have I read? Not much that directly addresses this. But what does suggests this is normal, and part of it is definitely in the brain, not the tissues. However, it is also apparently normal to require more or different stimulation to reach climax than previously. This in turn I find means that it can be harder on the physical parts and I find that may require more recovery time. (Makes sense to me, given nerve damage, trauma, and/or retraining)
@philipsnowdon I've wondered if I'm low testosterone, and my urologist is willing to explore this, but I don't have your challenging history, and I've been reticent to consider testosterone for fear it might feed the (currently latent) cancer which I assume is still lurking somewhere. Maybe if I'm still stable in another 5-10 years? One day at a time.
As of now, I haven't had sexual intimacy using a pump and ring, although I've tried self stimulation with this combination to learn. Based on this, I think this would be different, but not necessarily preferable. I was using trimix, but my wife found it inhibiting because the arousal was so immediate and the injection process was not itself pleasurable or intimate. I found that while I had a firm erection, it also led to more discomfort or even painful tenderness, so we switched to accepting hardness insufficient for penetration for a while and now we have added sildenafil (viagra) which I wasn't able to tolerate earlier because of side effects, but seem to be able to tolerate now. With sildenafil 100mg arousal is maybe just good enough (6 on a 10 pt scale?) It's been about 2 months since we last used a trimix injection.