No official LineageOS support according to https://wiki.lineageos.org/devices/. And no, missing vendor support is still an issue even with Lineage support, as soon as firmware (and sometimes driver) updates are needed.
I would be all over the Unihertz stuff if that wasn’t the case. I see people talking about Lineage working, but I haven’t looked into it.
My ideal phone is something small and rugged with physical keys that supports Android Auto for navigation and a few other basic apps I need (Bitwarden basically).
I’m not completely against it yet, especially if it looks like I can use something like Lineage.
Software aside, I’ve heard mixed things about the keyboard on the Titan. Keeping an open mind though, I would like to support companies filling this niche.