I’ve found that being direct, but polite works well enough.

“Not to be rude, but I have to get this task done ASAP. Can we pick this up at another time? Thank you.”

Making more frequent, smaller trips might make it less of a pain? Maybe stop by the dumpster if it’s on the way to/from a daily route you need to take?

Find the owner and tell them the cat is shitting on your property. If they tell you to pound sand, call city/county animal control to see what your options are. Alternatively, pick the shit up before your robot lawnmower runs it over.

Thanks for the update and the work you do! Lemmy.world introduced me to the Fediverse and it’s been awesome watching the site grow.