Chrome and Edge 124 on desktop have already rolled out quantum resistant key agreement via Kyber for supported websites (largely just Google and Cloudflare hosted).
- Chromium Blog: Protecting Chrome Traffic with Hybrid Kyber KEM
- Test page here: https://pq.cloudflareresearch.com/
Vanadium, Mulch, and Mull do this too on Android since a few weeks now.
You can enable it in Firefox by setting security.tls.enable_kyber to true via about:config.
Signal and SimpleX also use Kyber as part of E2EE:
- Signal >> Blog >> Quantum Resistance and the Signal Protocol
- SimpleX blog: SimpleX Chat v5.6 (beta): adding quantum resistance to Signal double ratchet algorithm
Mullvad also supports similar:
Fedora/Red Hat also has some experimental stuff to work system wide:
There is little downside to layering the current crypto with eg. Kyber.
If it works, it works. If it doesn’t, the only thing wasted is a bit more bandwidth.