Currently I have an HTML signature for my work account on Thunderbird desktop that contains some simple text formatting and a logo image, but pasting the same HTML into the signature setting in K-9 Mail just inserts the HTML as text into the email.
I think supporting WebSerial (even if behind an about:config option to reduce attack surface for the users who don't want or need it) is required to compete in the 2023 browser market. I hate having to switch to Edge every time I need to use it.
