Well, it's most associated with anarchism, although I suppose you could try to fit the economic philosophy to some kind of radical socialist classical liberal limited state.
In general, you might get mutualism from syndicalism, especially syndicalism adapted to more decentralized economies, or you might get mutualism from land reform.
If, in Russia, the Left Social Revolutionaries were more organized, they might have been the dominant force after the October 1917 and/or July 1918 uprisings. In this case, it's hard to see Marxism-Leninism becoming the dominant left-wing-revolutionary philosophy, or subverting/suppressing opposing revolutionary groups. It's possible that, in China, non-Marxist socialist movements would have been the main opposition to the Guomandang. But it's hard to be sure which ones or how they would develop.