Yes! You can use any soap with the ENSUITE Shower Base. Just keep in mind that the filter is designed to catch dirt and debris, but it won’t remove soap.
If you’re recirculating water through your pump and HOTTAP, it’s best to flush everything through with clean water once you’re done.
Because removing soap from water needs specialised filtration systems (which aren’t really suited for camping), most campers either avoid reusing soapy water or make sure to give the HOTTAP a good flush after each use.