Board Thread:LotR Mod Technical Support/@comment-2602:306:CDAD:88A0:E9C2:9349:8830:F9E1-20171015082142/@comment-27219153-20171015182115

I would suggest you try it out first. That's the best way to find out if it conflicts or not.

You could also contact HubToo who has used the millenaire mod extensively, although I'm not sure if he ever used LOTR and the millenaire mod together.