Things should be concretized a bit...
What exactly device do you have? The title of topic is M9Splus, you are writing M8Splus below.
Also, it doesn't irrelevant if it's an OTT M8S+ (S812) or a Mecool M8S Plus DVB (S905*).
For the second device, I’m not surprised that WiFi doesn’t work because there is no open source driver for the SCI 9082C chip, so it won’t work with anything other than the factory Android.
Furthermore, which version of LibreELEC did you try?
Edit: Even in addition to the above, there are a couple of types of products called M8S-Plus, so it doesn't irrelevant how the name is written. A photo of the box (especially the insides) might be simpler.