PLEASE cross-sign with another older CA before the 9/2021 deadline

[schoen]

I don't mean to suggest this would have a huge impact, or even necessarily a measurable impact, but there's a campaign to send people to this site if you detect they're using outdated browsers:

https://browsehappy.com/

(I think commonly with a banner that suggests that it will benefit them, not with a mandatory redirection.)

[Osiris]

You might want to disable the HTTP to HTTPS redirect for browsers known to be incompatible, otherwise they'll see a certificate error even before the browsehappy notification.