For Android, if you happen to use Keepass as your password manager, I really like KeePassDX[0]. If the camera app you use doesn't support QR scanning, though, you'd need an app for that (and I don't think any FOSS camera apps implement this, as for as I can tell).

This one[1] seems the most up-to-date, by a German research group. You'd share the link as text to the KeePassDX app, search for the entry it's for, and it populates it with the HTOP/TOTP secret.

There are iOS Keepass clients that support this as well, though from what I can tell there's some drama with source code[2][3] in the landscape.

[0] https://f-droid.org/en/packages/com.kunzisoft.keepass.libre/

[1] https://f-droid.org/en/packages/com.secuso.privacyFriendlyCo...

[2] https://github.com/MiniKeePass/MiniKeePass/issues/606

[3] https://keepassium.com/articles/keepass-apps-for-ios/welcome...

And other allegations under the ethics & transparency sections of KeePassium's list of iOS alternatives https://keepassium.com/articles/keepass-apps-for-ios/