My red claw lived on fresh plants and cholla wood for almost 5 years
Many people who keep them in more aquatic environments feed them shrimp pellets. I kept a single female RCC in a 5 gallon brackish water tank with numerous brackish water tolerant plants. She did not like the shrimp pellets. She ate fresh plants and the cholla wood with a weekly shrimp pellet eventually. She re-arranged her entire primarily aquatic tank until it was cholla wood and floating plants (the better to pull them into the cholla wood to eat). She did not care for java ferns and java moss/willow moss at all. She enjoyed "exploring" Japanese moss balls (sticking her claws in them), but did not eat them.
It seems most crabs, and def my RCC, re-arrange their environment as much as physically possible to suit THEIR needs. Which makes sense. They are smart and if you just let go and let them live the way they want (even if this means taking them out of a beautifully scaped paladium), chances are you will have some very happy and thus entertaining and long-lived crabs. But they HAVE to have brackish water of at least 1.005 spg. An escape-proof tank. And they can not be crowded. Mine enjoyed some bumble bee nerite snails as neighbors and that was it for a 5 gallon. Maybe two females in a 10 gallon.
She recently died after almost 5 years. I miss that little critter and her brain that could always outsmart me.