QWEEDDYZ: No downloading any epicinstallers.
You need reinstall only with normal offline GOG installer. What yoy mean you "even downloading epicinstaller". What is is? What for? You do not need anything.
Reinstall it. And if you just start a new game - remove saves as well as all game fodlers, when reinstalling.
Did you buy this game? Looks like if you search third party installers - you dont have game buyed/
Just to be clear, for a little bit outdated version it should be setup_tropico_6_t6-610-winmaclin-gogec387cd_(64bit)_(52188).exe, for current one a little bit differ name (version is t6-#673-winmaclin-gog@a211c01 ). Do not disable integrity check checkbox in install settings (to verify bin) files and always check GOG digital signature valide for exe files!
For GOG Galaxy - reinstall and always do verify game files check after downlaoding. At least twice in a row (shouldt be any downloading, but Galaxy always redownload something).
Instal lgame to normal path, literally should be: D:\Games\Tropico-6\
Almost same for Galaxy cient itself.
Some issues tweaking possible described here (no guarantee for 100% correct)
http://www.pcgamingwiki.com/wiki/Engine:Unreal_Engine_4 the epic installer I tried because someone says unreal engine 4 needs to be update (my mistake).
yes, I did buy this Game by Gog and 17 others, I downloaded Tropic 6 again uninstalled the crashed game and removed folder Games and saved on USB HDD, and same problem.
I understand the above files, the integrity check checkbox is only available on Gog Galaxy, I have an Offline PC, I Love Gog because they still give me the option of freedom about playing games the way I want too, many games are early access , some updates are not supporting win 7 anymore, so I play an older version, "fine for me " (use Debian 11) This is a Personal opinion.
I contact Gog support, and see there is a new Tropico 6 version available will try this one.
thanks for you're feedback.