Some months ago, I used https://github.com/alexzorin/authy to export them. It basically creates a dummy-device to access the tokens, and then exports them to some format. But I have not figured out how to import them now into another app.
Use the plaintext export option on that project. Most TOTP apps should accept the URIs that are exported. Maybe not en-masse but individually for sure.
Ah, thank you, that worked in Aegis. I just missed the option for plaintext because of the long list of supported apps. So all it needs is a textfile with one otpauth://-entry per line and it imports them all at once.
I slowly migrated away from Authy when they decided to shut down their desktop authenticator. You can painfully export codes, though I generated new 2FA codes at every vendor.
I thought I had a lot of totp codes to migrate but then it turned out I didn't use many of them. After deducting them, there remained 10 apps that I needed to migrate. It took me an hour to port them to bitwarden manually.