You can flash plain OpenWrt on it and be as happy as you like.

But why should you be able to buy previous models? I don't get it. You can do, just buy them used. Sooner or later, the support will expire (so the device is not only end-of-sale but end-of-life) - but this is completely normal in IT.

You can't buy an iPhone 12 from Apple anymore.

If I remember right (@bruce) GL aims to provide 3 years of updates after end-of-sale?