I try to execute it manually in terminal, but output error is:

/usr/lib/polkit-kde-authentication-agent-1

New PolkitAgentListener 0x55fbb15fdca0
Adding new listener PolkitQt1::Agent::Listener(0x7f34780396c0) for 0x55fbb15fdca0
Listener online
"Cannot create unix session: No session for pid 2809"

• (process:2809): CRITICAL **: 12:20:33.145: polkit_agent_listener_register_with_options: assertion 'POLKIT_IS_SUBJECT (subject)' failed
  "Cannot register authentication agent!"
  Authentication agent result: false
  Couldn't register listener!

i am guessing that none of the parabola devs have a system setup with KDE, much less openrc+KDE - this could take some experimenting

off-hand, i can say that you probably only want to have one polkit package installed - i probably does not matter which one (at least that is my experience with the ones ive used such as gnome-polkit and lxpolkit)

I am seeing similar errors, which may be related, in Mate (x86) with OpenRC. I have tried running two different polkit agents (Mate and Gnome) from the terminal and they both give similar errors:

(polkit-mate-authentication-agent-1:24207): dbind-WARNING **: 07:13:53.904: Couldn't register with
accessibility bus: Did not receive a reply. Possible causes include: the remote application did
not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or 
the network connection was broken.
Cannot register authentication agent: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot 
determine user of subject

Looks like it may be related to this question that looks like it was posted on Stack Exchange by Megver83 ~3 years ago. Maybe he knows something about it?