setupWebauthnClient

Firefox:

# Setting needed by Google for enrolling
security.webauth.u2f = true
security.webauth.webauthn = true
security.webauth.webauthn_enable_usbtoken = true

# Setting needed by GitLab for login
security.webauthn.enable_uv_preferred = true

# Linkedin uses something called the "WebAuthn Conditional UI"
# https://www.corbado.com/blog/webauthn-conditional-ui-passkeys-autofill
# https://www.corbado.com/blog/linkedin-passkeys
# Which alone is the following setting
security.webauthn.enable_conditional_mediation = true
# But this is coupled with "autofill"
# https://web.dev/articles/passkey-form-autofill
# Which needs to be enabled under about:preferences#privacy
# "Passwords" > "Ask to save passwords" > "Fill usernames and passwords automatically"
# This is the equvalent of the following two about:config combined:
signon.rememberSignons = true
signon.autofillForms = true

Chromium:
# https://tuxcare.com/blog/passkeys-on-linux-breaking-free-from-platform-lock-in/
# This is an old flag, but might still be needed:
# Enable WebAuthn API
chrome://flags/#enable-web-authentication-platform-api

# Linkedin wasn't working for a while but somewhere on the way,
# the right click > "Use passkey from another device" started to work.