

Your options are mostly UBTouch and PostmarketOS. Due to how PMOS is designed, it doesnt fully function on the phones it supports. UBTouch does work well due to the ability to use a driver compatibility layer with android IIRC, but you still have the issue of needing a phone that can support it. (I think the latest pixel UBTouch runs on is the 3?)
also, the security model of mobile linux is nowhere near what android is. Things that keep android secure like verified boot are not yet implemented on linux phone OSes AFAIK
What do you mean by webview? If you mean the entirety of webview then no ROMs do that AFAIK. android would be broken without it. If you mean replace Google’s webview with their own version, I’m pretty sure all the ROMs I listed there do it. I didnt fact check it though so feel free to prove me wrong