I'm seeing this on a few recent Ubuntu 20.04 installs and trying to see if this is still my fault in some way, as the Internet is (yet) still silent about this..
root@hz-hel1-1-ci1:/tmp# GIT_CURL_VERBOSE=1 git clone https://gitlab.gnome.org/GNOME/gnome-2048.git
Cloning into 'gnome-2048'...
* Couldn't find host gitlab.gnome.org in the .netrc file; using defaults
* Trying 8.43.85.27:443...
* TCP_NODELAY set
* Connected to gitlab.gnome.org (8.43.85.27) port 443 (#0)
* found 387 certificates in /etc/ssl/certs
* ALPN, offering h2
* ALPN, offering http/1.1
* SSL connection using TLS1.2 / ECDHE_RSA_AES_256_GCM_SHA384
* server certificate verification failed. CAfile: none CRLfile: none
* Closing connection 0
fatal: unable to access 'https://gitlab.gnome.org/GNOME/gnome-2048.git/': server certificate verification failed. CAfile: none CRLfile: none
git can't even connect. I see this on all https hosts who have a letsencrypt certificate. I suspect this is related to the root certificate expiry today, but as far as I understood it should affect things like Centos 7 and other older devices, not Ubuntu.
curl itself works fine, i'm still chasing down git's dependencies here to narrow it down.