Ok, just a little RIBnet jesting.
I think you’re always gong to struggle with the combo of a matt finish and black tubes which are going to suck in and show every bit of cr@p unless you want to spend far more time cleaning the thing than ever enjoying it.
Hence the time machine comment, matt black looks lovely in publicity shots at a marina but is very impractical if you’re OCD about pristine looks every day.
Obviously there are treatments that can be applied but again on matt Hypalon it’s going to probably affect the sheen or lack of?
Short of dumping a load of chemicals and cleaners in the water everyday not sure what to suggest other than elbow grease and lots of scrubbing but bio degradable cleaners would be nice. The equivalent of Fairy Power Spray etc.