But also during the years I had (1 or 2) weird surprises: no seed was provided so I can save, only the QR code.
I know what you mean. I noticed this on an exchange I was forced to use occasionally many years ago. I've migrated away from Google Authenticator (many months ago) and I am since then a happy Aegis user 
Google Authenticator now allows users to create and download a backup of their codes. Were you able to import this backup into Aegis or did you add the 2FA codes manually? Also, can Aegis be used all over the place same as Google Authenticator or does it come with some limitations? I am considering using Aegis myself, so it might be good to know.