I always backup my TOTP secrets to a file on my computer. Android apps like Aegis can automate this, by having an encrypted export to a file anytime you add or change a secret. You can use {Nextcloud, syncthing, etc.} to maintain that export file current with your computer.

If your phone is stolen, you can generate codes manually using a TOTP utility, or by restoring the backup to a new/old phone.