This is almost true for anything which isn't open source. .
For a lot of people if not everyone , their belief lies in reputed and "trusted" companies. I would recommend staying away from Authy, but if you are to use it then make sure to turn off multi device in the settings. This prevents recovery from other phones. If you ever want to transfer to another phone though this option will need to be enabled.
Any particular reason why? I have been using authy and I say it is any day better than Google authenticator, for it doesn't BACK up your fucking data. Almost had a nightmare when I un-installed it by mistake, had to contact so many exchanges to remove the 2FA 
I personally have never had any issues with authy.
You can use a USB like U2F Zero as long you don't lose it you're good to go https://www.u2fzero.com/
... and it's open source https://github.com/conorpp/u2f-zero
Is this any good? I'd love to buy one but the USB looks too old-fashioned and doesn't have a case supporting it, possibility of it to break easily is also a thing to be taken into consideration before buying it. ... and it's open source https://github.com/conorpp/u2f-zero