How can I tell which of my two network cards is currently active?

My integrated network card (NK) from the notebook is weakening. For this reason, I bought a wireless USB adapter and use it. However, I want to make sure that I only use WLAN via the new NK and no longer via the old one.

How do I check this?

You could simply deactivate the onboard Wi-Fi.

Go into the adapter settings and deactivate the other card.

Settings → Network and Internet → Change adapter options