I'm struggling too with such case and with other cases as well, for example: supporting iOS 14 and 15 in a project with deployment target set to 14, and if I want to use an iOS 15 modifier I need to either:
use #available checks everywhere in the code, ending up with hundreds of these which's so bad practice.
or create a new view modifier for each iOS15 modifier I want to use, in which I check #available between 14 and 15 versions.
I created a new question describing the problem on SO.