Any recommendations for a "gym" App?

Try JEFIT

Does Massive from F-Droid work for you?

I use Jefit, you'll get asked to upgrade to the paid version but I find the free version very usable.

I have been using JEFIT for years. One thing that I like is that you can use their website to modify or create workout plans.

I also didn't get on with Garmin for strength work. I moved to 'Strong' on Android - everything I was after is at free tier.

Boostcamp is great for this, plus it has tons of programs already set up

I have used Jefit for what feels like 10+ years now and I'm satisfied

RP Strength. Not free, but it's good.

I use a table in Obsidian. More manual but adds flexibility such as easy direct note taking, linking to videos of exercises, etc.. I use syncthing to keep version control and sync between devices for stats on home pc. Also very private in terms on data(thigh not necessarily encryption).

Liftosaur. Super customizable to the point of being programmable.

For watches I like GymRun. I don't take my phone into the gym and the watch functionality mirrors the mobile app on my Samsung and on my Garmin when I had one. Sets, reps, routines, rest time, etc. The main drawback for me is it doesn't sync with Strava natively so I have to sync with S Health which syncs with Strava. Logging your routine is necessary with progressive overload, and this beats pen and paper.

Don’t use BodyFit by bodybuilding.com.

Their developers are completely incompetent and break the app haphazardly. Earlier this year, they broke the ability to login. So you could not use the app at all.

Do not use BodyFit. Yes, I’m salty that it broke between two sets and my workout was ruined for the day and then also for the week.

Progression has been my absolute favorite.

Reddit fitness user made it back in the day, works perfectly, super customizable without any terrible subscription.

There is a companion body composition app for tracking measurement changes.

Best app I have tried to date except for a while the rest interval alarm would sometimes make podcasts get stuck at a lower volume, but android auto had that problem too, so maybe an android thing.

Only thing it is lacking is heart rate tracking from a Polar strap for example.

I just paid for Fitbod after the trial. It's basically a smart dynamic workout program app that tracks muscle usage and creates programs on the fly with recovered muscles. It gives much needed guidance on what to do, and explains every exercise, with total customization for everything you do.