I am able to play it at 49-60 fps unlocked fps with some pretty noticable hitches. I was able to achieve this with
-720p
-Playing offline
-Turn off fram sync and screen tear on the deck
-Medium settings all turned on except textures at extra.

I will say even when capping the fps at 45fps I still get hitches on the map but I get that on my PC that has a 3070 and a Ryzen 7.
The map is pretty unoptimized but that is normal for custom maps because there was no proper documentation.

i have several fps drops playing on steam deck, going down to the 35 fps in some points, for some reason this game fells realy bad when u play under 60 fps.
anyway even my pc is struggeling to get 60 fps on this map in particular i think the map need a little performance update

The map plays pretty well for me when I make a few changes to the Graphics. Lowering the Render Resolution to 70%, changing the Texture and Mesh Quality to Medium, disabling Motion Blur.

The fps will still drop to 50, maybe slightly lower; but it's the best options I've found to play it on the deck.

Something I assume would really help fps is boot the game on windows and use the t7 community patch. I just found that helps my fps even on PC.