I’ve been running mavic 819’s for 3 years. Simple to the fit tyres, I’m a serial tyre changer so tended to run without sealant (you will need to top the air up a bit more often without sealant).
The only flat I ever had was from a very shonky landing on a DH track with an XC tyre (High Roller LUST) which ripped.
I’ve fitted UST tyres to normal rims (+tube) without any issues.
I think the main difference between a UST tyre and normal tyre is that the UST have thicker sidewalls. Yes they are heavier but they are lighter than the eqivalent tyre + tube combo.