QUIC is a protocol, initiated by Google, transporting HTTP over UDP. It is more efficient than HTTP/2, which uses TCP. Chromium-based browers should support QUIC, it should be activated by default. Firefox and Safari support QUIC, too, but maybe it is not acitvated by default.
Some webserver implementations support QUIC, but the popular Apache webserver does not. QUIC uses UDP port 443.
In Meraki environments, QUIC will bypass the content filter rules on the MX. You can block QUIC in the application firewall on the MX. This will force the applications to TCP/443, and the content filter works.