My laptop does support this feature since it was working on Fedora KDE. But jumping over to arch, it seems not to work at all.

1. power-profiles-daemon.service is enabled and running.

● power-profiles-daemon.service - Power Profiles daemon
     Loaded: loaded (/usr/lib/systemd/system/power-profiles-daemon.service; enabled; preset: disabled)
     Active: active (running) since <time>; 12min ago
 Invocation: 4f20b3d144584a759b4a6c5ea14aa739
   Main PID: 608 (power-profiles-)
      Tasks: 4 (limit: 6850)
     Memory: 1.6M (peak: 2.8M)
        CPU: 81ms
     CGroup: /system.slice/power-profiles-daemon.service
             └─608 /usr/lib/power-profiles-daemon

Apr 18 11:14:52 berserk-arch systemd[1]: Starting Power Profiles daemon...
Apr 18 11:14:52 berserk-arch systemd[1]: Started Power Profiles daemon.

2. plasma-powerdevil.service is static and running.

● plasma-powerdevil.service - Powerdevil
     Loaded: loaded (/usr/lib/systemd/user/plasma-powerdevil.service; static)
     Active: active (running) since <time>; 12min ago
 Invocation: 7d72f24a0e5e4a74889a3895b91eb51c
   Main PID: 1074 (org_kde_powerde)
      Tasks: 9 (limit: 6850)
     Memory: 10.6M (peak: 11.4M)
        CPU: 1.391s
     CGroup: /user.slice/user-1000.slice/user@1000.service/background.slice/plasma-powerdevil.service
             └─1074 /usr/lib/org_kde_powerdevil

3. upower.service is enabled and running.

● upower.service - Daemon for power management
     Loaded: loaded (/usr/lib/systemd/system/upower.service; enabled; preset: disabled)
     Active: active (running) since <time>; 12min ago
 Invocation: 7aa43a43146346e383c961ce12cc9ded
       Docs: man:upowerd(8)
   Main PID: 540 (upowerd)
      Tasks: 4 (limit: 6850)
     Memory: 5.1M (peak: 5.9M)
        CPU: 251ms
     CGroup: /system.slice/upower.service
             └─540 /usr/lib/upowerd

I've already tried to to put

GRUB_CMDLINE_LINUX_DEFAULT="amd_pstate=active"

as a kernel argument that doesn't seem to do anything as well. I can't figure it out. The power management settings work tho. Any idea what's wrong? Thanks.