As a non-tech user I found your description on Google Play Store fairly opaque.  If you could use some sentences without jargon perhaps more people would download your app.

I particularly want to know whether I can use the app with Dropbox, Lastpass and Google.  If it's true you could add a phrase such as "FreeOTP works anywhere that Google Authenticator does" to your description.

I'm afraid that I don't know what 'TOTP' means, and I don't want to.  Please excuse my being blunt but,  I want to make the point that there are probably millions of people with the same attitude.

How often do you update the app? Duo claim on their blog that they update their app every month or two and that this makes them better than Google Authenticator.

Best wishes for the success of your app,
aka Catbells on Ubuntu Forums et al.