As previously mentioned, you may be able to install a proper Linux distro instead of Chrome OS and continue recieving updates that way.
That said, I'm assuming you are not tech savvy and need nothing more out of a computer than just browsing the web, if you're using a Chromebook in the first place. So maybe that would be a waste of time and energy for you.
You got 7 years out of that, so maybe plopping down another $200 on a fresh one wouldn't be too crazy. You could go with another Chromebook, or go back to a Windows laptop, there are some dirt cheap ones in similar price ranges to Chromebooks. Either way, 7 years out of a cheap computer is good.
Sure, you can get a longer life of a computer, especially higher-end ones - for example, my aunt and mother both use laptops with 3rd-gen i5 CPUs. So 2012-2013 era. Both of those had RAM upgrades, the HDDs replaced with SSDs, and Windows 10 installed, and continue to survive for basic web browsing needs. But next year when Win10 officially reaches end of support I think it'll be time to replace both of them and I'll take them laptop shopping together.