Your smartphone I.e samsung galaxy m12 is a 2021 model which was last in it's class to have 2.4Ghz only wifi m13, m14, m15 all support 5Ghz wifi. I don't know if dual band was not as popular at that time but at the present samsung has provided most of its latest smartphones with dual band the only exception being F0X and M0X series this would not take long as even A05 has dual band. Also dual band wifi is not a software only feature which can be added via any update the smartphone needs to have specific hardware too which is why regrettably to say your device can never support 5Ghz Wifi.
