Leave the rhubarb to die down naturally, some people leave the leaves in situ to feed the plant, personally I remove the leaves when they’re dry & shrivelled & replace with a good mulch of well rotted manure around the plant but not over the nobly bits that you can see. You might want to move a few strawberry plants nearest the rhubarb as it will get bigger next year & shade them out & now is a good time so they settle in for next year.