I run start.sh for stardew valley and get this :

---------------------------------------------------------------------

Running Stardew Valley
./StardewValley: line 7: sw_vers: command not found
NoFpsCap: This feature is not available
setGameMode( 'titleScreenGameMode (0)' )
loadPreferences(); begin - languageCode=
No usable version of libssl was found
./StardewValley: line 27: 4136 Aborted (core dumped) ./"Stardew Valley" $@

---------------------------------------------------------------------

but libssl3 and libssl3(i386) are installed already according to my package manager...
can someone help?

You could try this:
https://www.gog.com/forum/stardew_valley/linux_no_usable_version_of_libssl_was_found/post3