I like this little book. It’s waterproof paper and you can take it with you. Kinda pricey, but still cheaper than the online plans.
Swim Workouts for Triathletes: Practical Workouts to Build Speed, Strength, and Endurance (Workouts in a Binder) https://www.amazon.com/dp/1934030759/ref=cm_sw_r_cp_api_i_NTYQSDSPV557GKDB0GWA
Join a masters club, you wont regret it.
There is a person that has posted many masters workouts. Search "masters workout" for this sub.
I also recommend swim workouts for triathletes. I used this book until I joined a masters club. I have been snagging workouts from it, the person posting masters workouts, and some from masters coaches on my team during Covid.
https://www.amazon.com/Swim-Workouts-Triathletes-Practical-Endurance/dp/1934030759
Hey thought of one other thing. I swim with a team so I never use this anymore but this boom for Amazon was all I used for the first two years of swimming when I started triathlon. Swim Workouts For Triathletes
Great workout book I use when I can't make a masters workout: https://www.amazon.com/Swim-Workouts-Triathletes-Practical-Endurance/dp/1934030759
Another really good resource from u/cdowd9006: https://old.reddit.com/r/Swimming/comments/ooq4gy/721_wednesday_masters_workout_short_course_yards/
https://drive.google.com/drive/folders/1tHrMzBZWcVHQcs03vZX8rNQ73mdyR1j7
Another good option: Swim Workouts for Triathletes: Practical Workouts to Build Speed, Strength, and Endurance (Workouts in a Binder) https://www.amazon.com/dp/1934030759/ref=cm_sw_r_cp_apa_ZNy6xbPRZRBBQ
Grab your self a book..
( This particular one is all free-style.. but you should get the point )