OnePlus as of late have been lagging with software updates for phones that aren't their latest. The 7 series a day before the announcement of the 9 series got 11 "final", which apparently still has bugs which were in the betas.
Though with Samsung guaranteeing 4 years of security updates and have been updating phones to newer major android versions pretty quickly, perhaps consider an S20 or even the S20 FE 5G if you would prefer Snapdragon.