Aegis is a free open source TOTP 2FA app like Google Authenticator, and available on both F-Droid and Google Play. You should be able to export from Google Authenticator and import into Aegis.
Edit: I had assumed because Aegis had an option to import from Google Authenticator that this would mean you could export in bulk. Bad assumption to make, it sounds like you can do it if you have a rooted phone but Authenticator doesn’t make it easy. I did find this that shows a method to do a handful at once: blog.jay2k1.com/…/how-to-bulk-migrate-from-google…