As new to networking I hope for some overall advice.
The setup:
Have an LTE router which is running openwrt. It is to be placed in a well and connected to a plc. The data that is to be transmitted is very limited, like less than a kb maybe once a day.
I want to connect to the router and read the data. Should I use openvpn or sshtunnel, or just portforwarding. The data is not that secret, its about waterflow, if a pump is active etc.
The connecting PC will always be the same but have dynamic IP and so does the LTE router in the well. PC is running Win 10 and wmware Kubuntu too.
The need for NOIP I know, but will prefer not to use VPN account - both for payment and for learning networking.
Many cellular data providers do not assign a true public IPv4 address to the subscriber devices... hopefully yours does (or will if you ask/pay), or with any luck they give you an IPv6 address that is properly routable.
Assuming you have a way to reach the router over the internet, a local VPN endpoint is great. I'd recommend Wireguard instead of OpenVPN because it is easier to configure. WG is also higher performance, but that's not relevant in your situation. But either solution will work.
If you do not have a public IP on your LTE router, you could go the other way and have it initiate the connection (periodically or continuously) to the network of your connecting PC. You'll just need to setup VPN endpoints on the respective routers (or on the connecting PC).
If I go with the wireguard - it is actually an optional add-on in the menu of the LTE router - then I can choose either Windows or Linux on my laptop. Would you recommend one or the other?
Sounds like you are not using an official openwrt version, but glad that it has the option for wireguard.
I don’t understand your question about using windows or Linux. That is up to you. I prefer Linux over windows any day, but it really depends on what else is needed from that computer.
It is an Teltonika LTE router with a modified version of openwrt. Using cli it is surely based on Linux. Their OS is offering the ad-ons, like wireguard.
On the pc, which is win 10, there is installed Kubuntu on wmware. So I can choose to do it in Windows, which I am used to, or in Linux, which I try to learn. As I understand your advice, it is best to do it in the operating system I am most comfortable with.
In OpenVPN it seems like there are 2 ways of doing it, watching tutorials on Youtube, one is with a proces that involves keygeneration and one that seems much simpler but only needs a pasword. Do you have advice on this - if the more involving way is necessary or just stick to the easy way?
Again, thanks for advice - it means a great difference.