I confess that I don't understand your question. How is a tunnel involved?? But I'm not aware of any built-in feature to reverse the preference for ipv6 over ipv4. In case it helps: it appears you can add domain to an "ipv4-only" preference to bypass ipv6 for those domains. But this is only practical for a short list of sites. Here's how: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. ''More info on about:config:'' [[Configuration Editor for Firefox]]. ''The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.'' (2) In the search box in the page, type or paste '''network.dns.ipv4OnlyDomains''' and pause while the list is filtered (3) Double-click the preference to display an editing field, and add the desired domain(s) using the following syntax, then press Enter or click the blue check mark button to save the change: example.com,example.org ---- Perhaps you can run your own DNS service that returns ipv4 addresses preferentially? If you're not the only person who ever wanted this, maybe it's out there somewhere.

See also: *https://www.google.com/search?sa=N&num=100&q=prefer%20ipv4%20over%20ipv6 e.g.: *https://kb.firedaemon.com/support/solutions/articles/4000160803-prioritising-ipv4-over-ipv6-on-windows-10-and-11