For disabling 5 GHz I saw online (I no longer have the source webpage) that there was a modprobe option 5ghz_disable which when set to 1 would disable 5Ghz. Option appears to have been removed 6 years ago.
For disabling MIMO:
I tried setting ht_capab=[SMPS-STATIC] in hostapd.conf config file but was told it was an invalid option.
We are running in an ARM Linux environment
Wifi Module: iwlwifi
Any guidance you can provide regarding the proper technique to disable 5GHz and MIMO would be appreciated.