I should have mentioned that I've filed feedback. I don't think an actual bug report wouldn't be appropriate in this instance.
I have installed the recent "macOS Mojave Supplemental Update, Safari 14 with bug fixes" and tried again at the site where the Captcha was reliably not functioning. It now works.
Any idea when the Catalina update is coming?
The new Great Equalizer is the SEND button.
In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire
