I've tried, and had some success, using indexing shifters on derailleurs not designed to index, though its always been very fidgety. Now that I finally decided to go all in on indexing on one of my bikes I don't think I'll ever mix and match ever again. If I want a bike to index, I'll make the investment to get the correct shifters, cables, housing, cassette, chain, and derailleur. Otherwise I'll keep it all friction.