IPv6 does not have in-path fragmentation the way IPv4 does, and you cannot depend on an Internet MTU of more than 1500 octets.
IPv6 uses path MTU discovery (PMTUD) to discover the smallest MTU in the path, and it will send packets that fit in that MTU (IPv6 requires an MTU of at least 1280 octets). One way to do that is to have the source host pre-fragment the IPv6 packet using the IPv6 fragment extension header.
You could certainly send an IPv6 jumbogram, but it will be pre-fragmented in the host to multiple IPv6 packets using the IPv6 fragment extension header so that each fit into the smallest MTU in the path.
In reality, there are no data-link protocols that have an MTU even approaching the standard 65,575 (65,535 octet payload and 40 octet header) maximum IPv6 packet size, much less that of an IPv6 jumbogram, so any IPv6 packets larger than the smallest MTU in the path will need to be pre-fragmented.
The reason IPv6 has eliminated in-path fragmentation, putting the burden on the source host, is that puts a real burden on routers, and that slows packet delivery. Certain IPv6 features (fixed header size, no fragmentation, etc.) were designed to reduce the router burden, speeding packet forwarding.