I would highly recommend LineageOS. Supports non-Pixel phones, some of them many years old (although now that I double check, the Galaxy S3 and OnePlus One aren't on the devices list anymore, I guess they do stop supporting old stuff eventually...). The OnePlus 5 is still supported and was released in 2017. For anything older than that, I guess I'd recommend looking into postmarketOS.
reply> at least at the time, they only supported pixel phones
replyAt the time? They still are the only devices officially supported.
Having your freedom be tied to a handful of devices from Google, is a massive supply chain risk.