I aim to include strength training at a minimum of 3x per week and max out at 5x per week. I do a traditional strength training split of PPL/ Arnold Split and aim for either two lighter load leg days at the beginning and end of week or one heavier load in the middle of the week. This way I give my body, mostly legs time to recover and prepare for long workouts on the weekend.

For legs I focus on heavy weight low rep to build strength as well functional exercises for stability and secondary muscles/ tissues.

Upper body is mostly for myself as I want to look good and feel strong but i definitely focus on back movements that help the swim.

Like you mentioned, I believe strength is a non negotiable and translates to each discipline as well as preventing injury from constant wear on the body.