Personally I think Putin is very sincere. Russia has always used "agreements" as a way to buy time when things are going wrong for them on the battlefield, so as to permit them to rebuild and rearm in preparation for the next attack. So it's natural for Putin to seek such negotiations now, when Russian forces are in a poor condition and Western capacity to resupply Ukraine is diminishing daily. In an ideal world, enough naive Western politicians will gather round this idea to ensure (i) aid to Ukraine falls off, (ii) Russia has time to train and arm at least 500,000 conscripts while simultaneously rebuilding supplies of materiel, and (iii) Putin can present his "smart and stable genius" to his own people and thereby attempt to fractionally restore his shattered image.

We shall have to wait and see just how many spineless, ignorant, and naive Western politicians take the bait.