How to install 14.6.1 not 14.7.1

Work the Dexcom G6 app for tracking blood sugars, they're a bit slow on updating their end, and their app isn't compatible with the 14.7.1 update, my phone is still on one of the 13's, so now want to update to the 14.6 but it's only showing me the install option for the 14.7. Cannot for the life of me figure out a way round this, how do install the 14.6. Anyone assist?