Hi there,
I'm happy to report that in the most recent Royal TSX beta and the corresponding WebKit plugin we added SSL client certificate handling.
Like in Safari, your certificate must be stored in the Keychain and if that's the case, you'll get a prompt to pick the certificate to use when navigating to a website that requires a client certificate.
Please grab the latest Royal TSX beta from here and make sure you install all plugin updates. Then, please test the new feature by navigating to a website that requires a client certificate using the WebKit plugin.
Please let us know if it works for you!
thx,
Felix
Tianle Chen