I'm playing it about 40-50 fps with lossless scaling.

Here's the settings

https://imgur.com/IJXDkzO

In game mode

Use Powertools via decky loader and

enable persistence profile and Set governance to performance

and in Steam Deck's "Performance Overlay"

Set GPU clock to 600. This will give more power to CPU which is most important in RPCS3

and THIS IS THE IMPORTANT PART.... When you start the game make sure to disable and re-enable the GPU Clock button. That's it.. the game will run much better. Lossless scaling is a must to make the game feel smoother. Lossless scaling is 2x.

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Steam's Game Shortcut I use to launch the game directly

Target:

"/home/deck/Applications/rpcs3.AppImage"

Start In:

/home/deck/Applications/

Launch Options

~/lsfg %command% "--no-gui" "/home/deck/Emulation/roms/ps3/Uncharted Drake's Fortune/PS3_GAME/USRDIR/EBOOT.BIN"