The recent (Jan 25) update to the Gear Fit Plugin is causing issues with notifications. I no longer get notifications from third party messaging apps as well as notifications turning back on after I turn them off. I fixed the issue for now by sideloading the previous version (Aug 28) of the app from APK Mirror.
You have to uninstall the Gear Fit Plugin from your phone before it will let you sideload the older version. After that you will have to reconnect your Fit and go through the setup, but all your settings should stay the same.
Hopefully by sideloading the app it will prevent Galaxy Apps from auto updating it until a new version comes out with a fix.
Not sure if non-Samsung phones also use the Samsung Gear app. If it does, you could try an older version of Samsung Gear here: https://www.apkmirror.com/apk/samsung-electronics-co-ltd/samsung-gear/
On android you can get a third party that syncs with google fit. (https://play.google.com/store/apps/details?id=nl.appyhapps.healthsync)
The fit integrates with MyFitnessApp out of the box (well in app) as well and you can then tie that into a bunch of apps like Strava etc.
On iOS, you're kinda out of luck, unless you have a spare android or emulated android that you use just for syncing - (MyFitnessApp will then sync across systems and you can use that as a hub, but note that the Samsung Health app data absolutely doesn't).
I got this one from amazon yesterday https://www.amazon.com/gp/product/B01L6RB1XA/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
At first I had issues replacing it, the connector is kind of tricky but it worked.
I only got this because I noticed the band that comes with the Gear Fit 2 became loose. I have a large band and was having to move to the second to last hole from the third to last because it was loose and not tracking things properly.