if you installed the native linux version, you won't *have* an .exe
regardless, most of the information about ways to improve performance for this game is out-of-date anyway.
basic stuff like the game not actually detecting/utilizing GPU has been fixed for awhile now and mesa itself has had mesa_glthread default to true for years now, so changing that shouldn't effect anything
(on linux atleast, windows is famously a complete mess when it comes to multi-core utilization)
though, depending on your exact hardware you might actually see am improvement turning it off, to test that you can add
mesa_glthread=false ./Vintagestory
to the run.sh file located at /home/user/.local/share/vintagestory
BEFORE ANY OF THAT THOUGH
if say...you recently upgraded your GPU, do yourself a huge favor and make sure your bios is up-to-date. then, open it and insure that 4g decoding/reBAR support is enabled. if it's not, your effectively kneecapping yourself. enabling reBAR support is *mandatory* for pretty much any GPU released since 2020. exact boost varies heavily game-to-game but you should see an easy 10-15% fps in most games with it on, some games it's dramatic 50%+.
tested this with Vintage Story and it's the latter.
I have ryzen 7 5800X3D + 7900xtx
all settings maxed reBAR off, start's off struggling to 100fps, constant spikes down to <30. eventually bandwidth fills up and it slows down to unstable 40-30fps
all settings maxed reBAR on, easily hits 120-140fps, relatively frequent spikes down to 60, but that performance doesn't degrade.
reduce view distance to sane level and LOD bias to 80% or so and it's a constant smooth 144fps (my monitors cap)
changing vsynce to on+sleep should help with stuttering issues.
beyond that, all the average user can do to improve performance is turn on debug info (ctrl+f3), let the game load for a bit, then start lowering graphics settings till they reach desired fps.
the two most impactful settings for performance are "view distance" and "far geometry LOD bias", those 2 settings compound onto each other. with the latter being just how detailed far-off geometry is.
vintage is designed to run with a default view distance of 512 and LOD bias of 67%, ime view distances of 1024+ are especially taxing.
if you've optimized all the graphics settings and notice performance still gradually getting worse, you might just be having a heat-throttling problem.
this is very easy to check/fix thankfully, just grab whatever fan you have lying around the house, open up the side of your PC, then point fan towards case and turn on.
if you notice your FPS increasing/stabalizing after doing this, congratulations...you have an airflow problem, and need a better designed case/motherboard layout/stronger fans.
if after all that you still have weird stuttering issues...it's probably just a driver problem, and your sol until AMD/whoever pushes out some driver updates (moreso an issue for latest/greatest GPU's)