Absolutely, security updates are much more important than feature updates. Upgrading to newer Android versions is mostly useful to have access to newer Android APIs (apps eventually will require newer versions, although that usually takes quite a while). Another benefit of newer Android versions might be added security features.
Samsung’s update policy for their lower end models is pretty atrocious. While on paper they offer updates for a couple of years, it you look more closely, you’ll notice that the update intervals get larger and larger as time goes on. You might not get important updates for half a year. Sure, still better than not updates at all, but a pretty awful policy for security updates.
Fairphone is actually worse than Google when it comes to updates. Even their flagship phone is still on Android 13. Even the Pixel 6 runs Android 15 at this point and with this news it is guaranteed to get at least Android 17. Google has always been offering 5 years of support for the Pixel 6 and 7 series. What they didn’t promise until this announcement was additional feature/OS upgrades, but when it comes to that they were already ahead of Fairphone.
When it comes to alternative OSes, Google actually makes it very easy to install them. That’s one reason why GrapheneOS and the likes chose Pixel phones as their primarily supported phones.
For the Pixel 6 and 7 series Google has promised 5 years of security updates right from the beginning. What’s new here is that they now also offer feature and OS upgrades for that same time period. Certainly nice to have, but not essential.
Linksys WRT54G
The Linksys WRT54G did not run OpenWrt by default and the original OS does not even remotely resemble OpenWrt. What OpenWrt did use from the original OS was the Broadcom wireless driver because it was closed source (and a similar kernel version, so the driver could be used), since there was no driver in the mainline kernel.
But to try to answer the question, this device has been designed by the OpenWrt developers to fit their needs (and their users needs). Other routers running some variant of OpenWrt on them by default were designed by companies unrelated to the project. They most likely used OpenWrt because it was convenient to them. Their intentions weren’t usually the same as the OpenWrt team’s (repairability, easy to unbrick, etc.). Not that there is anything wrong with that. I like GL.Inet routers.
Unless you require the dynamic features of Wordpress, you could have a look at some of the static site generators out there (such as Hugo). Having a static site would reduce the attack surface considerably. Also due to the shenanigans happening with Wordpress at the moment, I would be weary of using it.
About SSL, what others have already mentioned, SSL certs are available for free these days, thanks to letsencrypt.
kWh is a unit of power consumed. It doesn’t say anything about time and you can’t assume any time period. That wouldn’t make any sense. If you want to say how much power a device consumes, just state how many watts (W) it draws.