Here to add on to this issue, it is not limited to proton pass. I use bitwarden with integrated TOTP in the browser extension. Bitwarden extension also cannot recognize the TOTP input field of kagi website. Meanwhile, bitwarden extension can recognize the TOTP input field of kagifeedback.org login page perfectly fine. I believe this issue has to do with how TOTP input field is presented.
Browser: Firefox, version 148.0.2
OS: Linux
TOTP provider: Bitwarden Extension, version 2026.1.1