I'm in the UK. My lawn is about 1/3 clover already, as it happens, just by natural process of it being stuff that grows better in the conditions on that part of the lawn. I don't consider that to be not-a-lawn, it's fairly normal I think, and the management is no different to the grass. (My 'lawn' overall is about 1/3 grass, 1/3 mostly-clover, 1/3 mostly-moss: the grass grows well on the sunny side, the moss beats out everything else on the side that's almost perpetually in shade by the south-side fence, and the clover wins in the middle-zone between them.)