I had a suuntu quest which had a comfier HR strap than my Garmin. Decent sized watch as well, bit irritating then when you start a workout, you lose the time. Worked with movescount app that linked to Strava sort of. Ended up exporting to FIT and importing. Worked great with spin bikes in the gym, but as above ^^ no protocol for phone based apps.
Decided I really hate HRM straps, so bought a fitbit surge HR. Yeah it’s not as accurate but I wasn’t using HR zones to train, I was just geekily interested. App is great as well. Can set up your own goals etc, log food if that’s your thing, more a lifestyle device than a training one.
Links well to strava and endo.