I use FreeOTP on mobile https://freeotp.github.io/ : it's another device than my computer (storing this on the same computer kind of defeats the purpose), Free, seems trustable, practical, works with all the sites that need it. (edit: link)
If you're importing the key into FreeOTP, you could just take a second copy of the key to store elsewhere too? TOTP keys are just short base32-encoded bitstrings.