A tiny % left and even among them there are many genocidal nationalists and fake opposition types.
Look up any research on the topic Russian Field, Levada, LSE List Experiment on support from the war among Russians.
I believe the general trend was that every age category had a majority and that at one point the 30-40 age group had slightly lower support for russian annexation and destruction of Ukrainian identity than the 18 -29 age group.