You can't install the LineageOS phone app (with more modern looks) on GrapheneOS, because:

- the package name is already taken and to replace app with the same name the package needs to be signed with the same key which you don't have

- even if you modify package name, it's a system privileged app, privileged apps may only be installed by Google/vendors (unless you're recompiling the OS [64GiB RAM needed])

- if you strip all the privileges, functions like call recording won't work.

Same for contacts and so on..