Depending on your intended use, running tubeless on a MTB has many advantages. There are three ways of dog so, firstly using LUST or UST tyres ona tubeless rim. The tyres are heavy duty, and form a perfect seal with the rim, which itself is constructed so as to be airtight to start with. UST or LUST tyres tend to have thick sidewalks and heavy tread area, and so tend to be heavy overall. IMO they are a bit outdated and with other friendlier technology, a bit unnecessary.
Tubeless ready setups next. These are rims designed to form a decent seal to start with, but using Tubeless Ready (TLR) tyres which have a soft flange to seal well into the rim. To use these, you tape the inner surface of the rim with thin airtight tape, fit a tubeless valve to the rim, then fit the tyre using latex sealant. The latex seals any air leaks in the tyre sidewall, and form a perfect seal on the rim. The latex remains fluid inside the tyre, and seals any subsequent punctures. At last count I had over 30 self-healed punctures in my rear tyre alone.
The third way is to use a standard rim and a tubeless rim strip. This is a rubber liner with its own valve which is stretched over the rim, and forces a better seal whe the tyre is fitted. They are a bit heavier than tubeless ready setup, but are a decent compromise. You also use latex sealant to deal with leaks and punctures. Yu can make a ghetto rim strip using a 20" BMX inner tube, stretched over the rim, then sliced open along the entire outer circumference, the tyre fitted, and any overlapping excess trimmed off.
The advantages of tubeless, especially TLR , are weight saving, albeit not so much with rim strips, and none at all with most UST or LUST tyres. Yu can however run much lower pressures in your tyres. I'm Clydesdale class, and run my tyres at 20 psi front, 25 psi rear which gives tremendous grip in most situations. If you were to run that low with a tube fitted, you'd get pinch flats on the first square edge you hit. The tyres also fel different without tubes. There's less squirm, and more even support. I've already hinted a the main advantage, which is self-healing punctures. Between the two bikes I run I haven't had to stop and patch or change tubes about 50 times. .......
