A new shared drop-in, packaging/linux/50-punktfunk-nice.conf
(user@.service.d, LimitNICE=-15), raises the user-session nice hard
limit so the direct setpriority() path works on rtkit-less boxes — a
limit, not a grant, effective from the next login. Shipped by rpm
(%files + install, flows into the Bazzite sysext via rpm2cpio), Arch,
and deb; the Steam Deck installer writes it to
/etc/systemd/system/user@.service.d instead (SteamOS /usr is
read-only), following its existing sudo-to-/etc pattern.
rpm and deb gain a weak Recommends: rtkit and Arch an optdepends hint —
with rtkit the fix needs no relogin at all. The NixOS module instead
sets security.rtkit.enable = mkDefault true (rtkit is not a given
there; mkDefault keeps it operator-overridable).
It remains true on every channel that the host binary must never carry
a file capability — the spec's no-caps note now names the two fallback
rungs instead of calling the thread nice a best-effort no-op.