There’s your trouble… I sh*t you not, I get better results for /e/ foundation stuff when I use DuckDuckGo instead of Google. Maybe this is the link you’re looking for? It was literally the first hit when I DuckDuckGo’d “e foundation teracube 2e”
The specific link you want for enabling OEM unlock is here. Scroll down until you see “Steps to enable OEM Unlock
through the command line” You’ll need a desktop/laptop with fastboot and adb installed to do this, but you need that for the rooting process anyway.
The instructions are pretty thorough, but I can’t vouch for them personally, because I ordered the “Murena” 2e with /e/ OS preinstalled. I did however install /e/ OS from scratch on my previous Android phone, so I’m happy to try to answer questions if you run into any problems…