I use it to wrap my gstreamer tcp streams in TLS to send them over the internet, but socat can also do the same thing.

Let me introduce you to software for public library information systems that still thinks it's the 90s!

I mean, most web application backends don't implement TLS at all, under the assumption that you're using it alongside a reverse proxy. Most of the time this is nginx, but if you want to ensure no bugs are introduced on the HTTP level by the reverse proxy, stunnel is a perfectly fine option.

I used it once with althttpd. https://sqlite.org/althttpd/doc/trunk/althttpd.md