Strava can auto-synch with garmin connect, which is free. So the steps are:
1) create an account with garmin connect, if you don't have one already.
2) test that garmin connect works fine with my app. There are currently no known issues here.
3) log into strava, go to settings, then choose "my apps" (it used to be "third party apps") and enable synchronization with garmin connect.
That's it. Upload to garmin connect from my app, and your activities will show up in strava. In my testing, it was pretty much immediate, but as usual with these things, there might be a small lag.
As I mentioned, if you buy a new garmin and get one that is designed to be used with a smartphone, it will only talk to the garmin connect app, so to get your stuff into strava you'll have to go through the above anyway.
Back on the sad news: the reason I'm not fixing the app right now is that 1) the app has never really been profitable, but it has plummeted to pretty much nothing in the past couple of years, as people choose to move to newer garmin models. It's hard to pour time into something that earns nothing. 2) I can't simply change the authentication code and push the new app to google play. Google now wants all apps to target android 9, and that requires sizeable changes into many areas. Due to (1), I really can't do it now. In the future, I may have to publish an APK that you'll have to sideload.
Bottom line: there is an easy workaround, please use that and enjoy your old garmin for a while longer : )