Personally, I don’t think Tuya-based plugs are a good starting point unless you can flash them with Tasmota and are already familiar with MQTT.
Let’s back up again. In the docs we talk about “openHAB” and “openHABian”. The latter is a customized version of openHAB that is designed for beginners (ideally with a Raspberry Pi 4), but is also used by advanced users since it has built-in extras such as MQTT and backup solutions.
You’re trying to reuse an old laptop, which is fine. However, you’ve installed Ubuntu even though you don’t know much about Linux. That makes it harder for us to help you, because you’re doing your own thing and don’t know your way around the OS you’ve chosen. So when you do post questions, you’re going to have to include a lot of detail about your setup and what you’ve done, so that others know the standard answers may not apply. And there are going to be some cases where we just might not be able to help you due to your unique system.
I’m not saying that you should go and buy a Raspberry Pi. Just that you’ll need to keep this in mind as you search more in the forum. Anything related to “openhabian” may not apply to you.