I haven't needed it for... probably 15 years, but in the past (before 3G was common, and all you could rely on was WiFi hotspots) I have used iodine[0] as an IP over DNS tunnel.
My uni friends were always impressed, and it really helped me a few times. The throughput was never great though, but enough for some basic browsing.
Edit you have to be prepared ahead of time though, and it's the main reason I bought my three-letter domain back then (shorter domain means higher throughput as payload is a higher percent of the query response).
I still find uses for iodine sometimes! Off the top of my head, a hotel basement with no cell service, and once on a flight. It's rare that it works, but quite entertaining when it does.
I think in one of those two (forget which), they just had udp/53 wide open (which works just like any VPN), but in the other, it had to do proper DNS tunneling. And to my surprise, it was entirely fast enough to be usable, which usually is not the case. I felt bad for probably bogging down their DNS server, but hey. (Kept it to a reasonable limit.)
The comment to which you replied was talking about networks where port 53 is open. But, given you were using iodide and you got slow throughout, I'm assuming you were on networks which blocked port 53 access to hosts on the internet, but allowed unlimited access to the ISP's own DNS server.
I haven't needed it for... probably 15 years, but in the past (before 3G was common, and all you could rely on was WiFi hotspots) I have used iodine[0] as an IP over DNS tunnel.
My uni friends were always impressed, and it really helped me a few times. The throughput was never great though, but enough for some basic browsing.
Edit you have to be prepared ahead of time though, and it's the main reason I bought my three-letter domain back then (shorter domain means higher throughput as payload is a higher percent of the query response).
[0]https://github.com/yarrick/iodine