Is it possible to connect remotely to a c-lightning node with an exposed TCP port?
EXPOSE_TCP is implemented in c-lightning's docker script:

https://github.com/ElementsProject/lightning/blob/2945b25b57db37dca31c10da34a4b1ca33d697c3/Dockerfile#L103

https://github.com/ElementsProject/lightning/blob/master/tools/docker-entrypoint.sh

If you didn't use that script or didn't implement it in your own docker script, it won't work.

It's easy to mistake EXPOSE_TCP for a parameter you can set when spinning up c-lighting.