I can confirm this fix works, but you need to set
GRUB_CMDLINE_LINUX="acpi_osi=Linux"
under GRUB in my case. Same laptop, same model number. I can only assume Donnarumma had it set while trying to fix some other bug.
Still, it takes a while for the battery applet to display that the laptop is on battery. The effect can be seen in the output of acpi -b a little sooner, though.
I can confirm this fix works, but you need to set LINUX=" acpi_osi= Linux"
GRUB_CMDLINE_
under GRUB in my case. Same laptop, same model number. I can only assume Donnarumma had it set while trying to fix some other bug.
Still, it takes a while for the battery applet to display that the laptop is on battery. The effect can be seen in the output of acpi -b a little sooner, though.