Hi @pormelrog, welcome to the Forum!
It’s very weird that you have different versions installed because PennyLane already comes packaged with the right version of lightning.qubit without needing to install it separately. My guess is that your system administrator installed it separately with a new version which is incompatible with your current version of PennyLane. That being said, in the plugins section of the PennyLane website you will find the built-in devices that PennyLane comes with. In the card explaining each simulator you will find a recommendation of when you should use one device or the other. We also have this YouTube video which provides an introduction to PennyLane devices, and if you want a more in-depth discussion of how to choose your device you can take a look at this article in the PennyLane blog. For what you need to do your best option is probably the default.qubit device. Normally I would recommend lightning.qubit but since it’s not working for you then default.qubit is a good choice.
Please let me know if this works for you!