PokerStars - $0.02 NL FAST (6 max) - Holdem - 6 players
Hand converted by PokerTracker 4

BTN: 76 BB (VPIP: 75.00, PFR: 75.00, 3Bet Preflop: -, Hands: 4)
Hero (SB): 100 BB
BB: 201 BB (VPIP: 0.00, PFR: 0.00, 3Bet Preflop: 0.00, Hands: 2)
UTG: 98.5 BB (VPIP: 27.27, PFR: 27.27, 3Bet Preflop: 0.00, Hands: 11)
MP: 108 BB (VPIP: 22.22, PFR: 11.11, 3Bet Preflop: 0.00, Hands: 27)
CO: 100.5 BB (VPIP: 18.37, PFR: 16.33, 3Bet Preflop: 8.33, Hands: 101)

Hero posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has J K

UTG raises to 3 BB, MP calls 3 BB, fold, BTN calls 3 BB, Hero calls 2.5 BB, fold

Flop: (13 BB, 4 players) T 9 3
Hero checks, UTG bets 6.5 BB, MP calls 6.5 BB, fold, Hero calls 6.5 BB

Turn: (32.5 BB, 3 players) 8
Hero checks, UTG bets 16 BB, fold, Hero calls 16 BB

River: (64.5 BB, 2 players) 6
Hero bets 31 BB, UTG raises to 73 BB and is all-in, Hero calls 42 BB

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Not much info on either villain but UTG seemed a little loose and fishy, plus he had the autonote that literally everyone seems to have of 'played turn draw aggressively'.

Wondering whether call/3b (/fold?) is best pre?
Peel one OTF with GS and backdoor?
Good turn for us so I think calling again is standard.

Not sure what to do OTR. Against a reg or at a higher limit I might x/r but I think I have to bet at 2NL vs a suspected fish. Slightly worrying when we get raised without knowing where A is but V has so many 2nd best hands that he could be overplaying here, I imagine.

If he seems loose and agro I would opt to let him bet again and x/jam.

I mean, I've only got 11 hands on the guy so that is a very shaky read.

Call pre is fine knowing we are often dominated.
Thinking calling flop is too thin, UTG is going to double barrel at a high frequency after betting into four people and lots of reverse implied odds with over overcards.

Donking river is good, villains checking back top/over pairs, two pair, probably sets at 2NL. I like sizing too aiming to get value from these hands too. This is quite exploitative though as we have few bluffs in this spot so keep this in mind vs better players.

I think river could get dodgy if you have a habit of doing this every time. If you lead out all your nutted hands on scary runouts what does it mean when you check?
But hand seems fine.
fwiw given the action, your blockers and the fact that flush is backdoor, the nut flush should be a non factor and you should proceed with the effective nuts.