For the later future Tropic Square could be interesting for what you want. Although, all the AOSP APIs would need to be developed for it in our use case (such as Weaver throttling, insider attack resistance setting and the Keystore) to have a smartphone that uses it.

More likely we'd have a new device from an OEM before the possibility of that.

The Pixels' RISC-V Titan M2 secure element is mostly derived from OpenTitan. Google committed to open sourcing the Pixel specific changes they made to OpenTitan a long time ago but it still hasn't appeared yet...