Shower is draining very slowly

I found a gadget at Home Depot. It's about an 18" long strip and has little "hooks" and you run it down and the hair comes back out with it! I dragged out a huge hairball (lol)that ya coulda made a wig with!

The drain screen should pop off with a little gentle persuasion ( screwdriver turn or pry). All the rv’s I’ve had came off .. most just snapped on but there’s all kinds of creative thinking on these rigs.??
Second you should have a inspection access to under the shower , perhaps something that looks like a vent in the base ? It’s almost impossible to work in the small space but access to the trap is why they put it there.

You could straighten a coathanger, put a hook on the end and put it in the drain to catch hair on the shower side of the trap. If no help try to get access to the p-trap and remove it to clean trap and drain line from trap to holding tank. many ties the hook till work without disassembly.