All of these recommendations are based on android/fdroid:

Bodyweight Diary: Trale https://f-droid.org/en/packages/de.quantumphysique.trale/

Workout Log: GymRoutines https://f-droid.org/packages/com.noahjutz.gymroutines/

Calorie Counter: Energize https://f-droid.org/packages/com.flasskamp.energize/

Breathing Techniques Breathly https://f-droid.org/en/packages/com.mmazzarolo.breathly/