I'm currently developing a couple of websites for a company that uses a VPN to share their staging servers.
Being in a VPN means that the url of my website is not public, and I cannot use browser testing services.
I want to ask how can I make some kind of tunnel that allows me to share a particular site inside the VPN to the outside world, so I can point browser testing services to it.
Is that a question suited for this site?
This is something you should first ask your IT, network, and/or IT security departments about. Whatever they're called in your company. We tend to take a dim view of anything that might be seen as bypassing security measures, and this may be such a thing depending on how you go about it.
If you do get the go-ahead from them, it will almost certainly be them, rather than you, implementing most or all of the necessary changes in the company network.
Things might be different if your company is small and doesn't have an IT department, let alone an IT security department. But in general if there is such a thing, you should go there first.
I'm not an expert on web services, but why not publish the URL online via a certain port or specific IP:80 and then setup firewall rules to only allow access from specific source IP addresses you are trusting for testing purposes?
As far as "is it on-topic"...that would depend on how detailed you frame the question, what you are attempting to do, what you've tried, and what options you are considering. It would also be helpful if you had full access/capabilities to implement any suggestions/answers given. But the community at large will help decide in the end.
The question is on-topic, although beware that asking questions about trying to defeat a VPN will yield answers about it being bad practice, but I do have a constructive answer for you, should you ask your question.
