Maybe they fixed this in the last 2 hours, but it works for me (firefox, linux).

Weird, it still says that "Cisco Umbrella Root CA" is not trusted. Maybe its only from certain countries.

I'm Canadian and in Canada for what it's worth. Clicking on the lock tells me that it was verified by lets encrypt. The root is "Digital Signature Trust Co." Common Name "DST Root CA X3".

Cisco sounds like a router might by running a MITM on you?

Edit: This looks to be confirmation that that root (or one by a very similar name) is used by a MITM tool:

https://docs.umbrella.com/deployment-umbrella/docs/rebrand-c...

Thanks for the diagnosis. Accessed from a different network and with no issues. And got the right certificate this time.

Same. FF/macOS

Hmm, interesting! Thanks for the report. I just ran it through Qualys SSL Labs and everything passed. (We got a B though because we still support TLS 1.1.)

It's a multi-domain Let's Encrypt X3 certificate and I believe most LE users will be in a similar boat now.