After the recent changes to debian-sources (5.14 being unmasked for next), the latest version is no longer unmasked for me with `sys-kernel/debian-sources **` in /etc/portage/package.accept_keywords.
Running a world update tries to install 5.10 again. Interestingly enough, specifying a specific version, e.g. `emerge =debian-sources-5.14*` works and Portage doesn't complain. Looks like it's just not being selected by default for some reason.