if you can get the xuid of the non ms accounts then you can put them in your /config/minecraft/permissions.json file, e.g.:-
[
{
"permission" : "operator",
"xuid" : "25350853"
},
{
"permission" : "operator",
"xuid" : "25378228"
},
{
"permission" : "operator",
"xuid" : "2536691926"
}
]