Does population fold flushes here?

So you're raising as a bluff. I just don't see better hands folding.

Im folding OTT. And I think opponent should fold flush unless he has a read on you.

Have heard that GG midstakes players are passive-call happy.

I dont think the right question is if he folds flushes here. Better question would be if he is realy checking back enough flushes.
I think his range is strongly weighted towards 9x so trips and just a very low amount of random flushes.
I also think that most of the stronger 9x will raise your block bet on the turn also there he could choose to go bigger with flush making it again more likeley to be something like A9 K9 type hand.
Also we need to consider that villain has A9 and K9 offsuited in his range from co so very different if he is in co or mp.
On the river he sizes on the smaller side he could overbet or potsize etc. this gives us another tell that makes him more likley to have not a flush and more often 9x.
Just a bit shitty that KK and K9 become full houses but you block them nicely.
So i realy like bluffing the river here vs a to capped range from population but one problem i see here is that you go all in and you dont rep much full houses.
Also if we attack a range that contain mostly 9x then we need to think about him having great blockers to our fullhouses so our valuerange and we can get catched pretty easy when polerising ourself to only full houses.
So imo raising the the river small like 3x gives us much better risk to reward so we are repping also some flushes so his herocalles with 9x become much worser and incase he has a flush or better we dont loose so much because anyway they dont fold enough vs all in i think.
And i like to have the q and k blocker alot because it blocks alot the more likley nutted hands like QQ, KK and K9 i realy dont care about flushes because they are to rare here

But all this is only as played ofcurse we need to ask ourself if we realy want to call turn. I think call is a fine option if you have the plan to xr him on the river because you think he has to many 9x hands and you punish his weaker sizings on the river by xr.
If you just call without thinking about this things and hoping to be good i dont like it. Alternativly we could also directly reraise the turn by blocking nutted hands like QQ and Q9 type hands looks very strong our line and dont think population finds enough bluffs in our shoes + the fact that they dont check back flushes i think great spot to just put pressure on villain and make him hate his life.
Fold would be ok if unsure call with no plan worst option

Flushes don’t X back flop.

He has 9x or a bluff so raise a sizing that folds out 9x. Jam is unnecessary.

i dont think he has flush, and likely 9x like what doo doo poker and giova said.

On this super wet board,

Potential Full House > Potential Flush > Potential Straight > Potential Trips.

his bet sizing here kinda more represents trips and sometimes straight as potential bluff. Which will fold to flush and FH

if he had flush I think its quite a marginal fold... he would call