I gave up with mine, ended up having to buy a replacement rear wheel, they seem to be designed as a stop-gap – they last just long enough to get from shop floor to the new owner and have a couple of rides before something goes wrong. OEM supplier, so they have no need to provide spares or customer support.
Hubs are normally either push fit (e.g. Hope) or the axle has some form of threading holding the end caps one. Take the cassette off and inspect the axle. I suspect you find two spanner flats on one end (disc side) and some way of turning the end cap on the other end. For QR axles the bore tends to a allen key socket so you use an allen key on one side and spanner on the other.
Play could be worn bearings or could just be the threaded caps have come loose.
The Whyte branded ones on my bike appeared to be Formula. Loose bearings, just needed a cone spanner.
Utter horseshit. Bearing surfaces were pitted after about 3 months riding.
The best bearing replacement I found was to use ones from a DT350, whilst also replacing the freehub with one from a DT350. As well as the hub shell, axle, and seals from a DT350. Since then I’ve had zero problems.
Formula: no focus onto the end-customer at all. Difficult to get information / spares.
I buy bikes with Formula hubs – and try to service them / re-grease them as long as possible. But I don’t spend too much time when there is “more trouble” (Formula is lousy quality) – rotten Formula stuff I replace with DT 370 hubs / custom wheels (if you like have a look at the configuration page from actionsports.de . This place I use to get my replacement wheels. Around 100 bucks for a wheel (in combination with FunWorks rims))