problem with internet connection both via cable and Wi-Fi. when Wi-Fi finds a network it connects and the internet is unstable or no internet. in my opinion, it connects and disconnects randomly, both when using a cable connection and Wi-Fi. Can anyone think of anything please?
I would start with explicitly disabling wifi when you have a cable connected.
Then maybe you can upload logs via MyOSMC - Log Uploader and share the URL for us to check
If you have problems with WiFi and Ethernet, it could be a problem with your internet connection. However you should disable WiFi as @fzinken says so we can check with a wired connection and ensure WiFi isn’t being used as a fallback
Sam