The chip was made by MediaTek and Google just provides Android and usually no firmware support in the first place… So how exactly is this related to Google?

Newer versions of Android were not available for the FP1. Older versions didn’t get the security updates. That was the issue.

That sounds like a browser issue which is unrelated to the OS.

No, it was not a browser issue. I don’t remember which one, maybe heartbleed, or any other of the famous vulnerabilities with a logo and a website.

Uhm what did you expect from a 1st generation smartphone made in 2013? That the software will always be up-to-date even 10 years later?

Well, that is exactly the claim, isn’t it? “The one that lasts” implies for me that it doesn’t randomly become unusable after a few years, even though the hardware is technically still fine. Smartphones have now reached a point of stagnating innovation. We already have most functionality we need, so it’s in theory a good time to produce phones that last until the hardware falls apart.