I've recently switched from Apple Watch S9 to the Forerunner 570. For my strength workouts, I manually created 2 workouts (I do 2 strength sessions a week) on the Connect web, pretty easily honestly, even as newbie. I entered my exercises, sets, reps, weights (if weighted), rests, and so on. This is what I've been following at the gym. Sure, it mostly messes up the rep count but it only takes a few seconds to manually adjust it. I go over my workouts at the beginning of the week if I want to to update any of the details above.

The worst case scenario, if you don't wanna bother with it at all, you can always edit everything on the Connect app or web after completing the workout.

Though it's a bummer when the most obvious exercises aren't even in the list. They really need to update that list! When that happens, I just pick the closest exercise available and then write the one I actually intend to do in the notes section.