Setting system refresh.timer on system boot

Hi! Using custom build ubuntu-core image, i need to set system refresh-timer to managed.

I tried to do it in one of the snaps, installed in the image, in configure hook, via calling sudo snap set system refresh.timer=managed, but got permission denied error (same w/o sudo).

That snap has snapd-control interface.

Is it possible, to set system refresh.timer to managed on system startup? Maybe using gadget snap, or smth?

Thanks!