writes:

If you were to have looked at the certificate, you would have found
that it was issued by USNS by the organizational unit NAIMES.

I did, and that was the name on the certificate.

USNS is the United States NOTAM System.

NAIMES is the National Airspace System Aeronautic Information Management
Enterprise System.

To put it simply, the certificate is self-signed by the FAA.

Actually, you don't know who created the certificate. Anyone can create a
certificate with any name. That's why you need to get the certificate from a
trusted source.

However, since these sites are not critical for me, I just added the
certificate, even though it wasn't possible to verify its origin.