I think tope can be used sometimes, I am not really sure and I would like to know the opinion of native speakers. Perhaps, the perception for mud is different in Bantu languages and the plural form is more used in general events or as collective noun. The singular form perhaps is less frequent and used to describe a piece of mud or other descriptions.
Here is an example sentence with tope:
“Hata nikilala kwenye tope hili, bado nitapata usingizi wa kutosha kuliko nilikotoka.”
“Even if I have to sleep in this mud, I will sleep better than I did where I came from.”