Funny to bump in to you here Henri! Ever since Authy's data breach a mere month after your post, I have been thinking of moving from Authy. They have since however made this next to impossible:
This is more secure, of course, but seems awfully convenient when so many are trying to migrate away after the data breach.
If you're curious, a solution to export keys now is to use a rooted phone and dance around the Play Integrity API used by the Android client. I have confirmed that this works, but the majority of people would probably just have to set up 2FA manually for each service if they want to move away...