Just done a tubeless conversion on mine.
X719s with Michellin 2.2 DTC All-Mountain tyres.
Bought 2 Schwalbe 20" tubes with the threaded valve stems & a small bottle of JustRiding Along wheel milk.
Slit along centre of tube, stick valve through rim hole & secure with collar, stretch tube around rim allowing it to fold over each side.
Put tyres back on.
Loads & loads of soapy water around tyre bead.
Remove valve core.
Pump up QUICKLY while pressing tyre against rim at valve point to help seal.
Once some air is in continue pumping QUICKLY until you're completely fecked.
Remove pump. Turn wheel 30 deg.
Add 50ml wheel milk.
Re-insert valve core.
Keeping valve at 9pm / 3pm so liquid is in bottom tyre pump again QUICKLY, pressing tyre against rim to help seal.
Give wheel a good sloshing round so the milk starts to seal. You'll hear the air leaks start to go quiet. You'll also notice wheel milk leeching out from various points all over the tyre.
Eventually it will seal completely.
Did both of mine last week & both are still rock hard.
Pressing tyre against rim at valve point seems to be the key.