The Lua.log can be found in your "..\Documents\my games\Sid Meier's Civilization VI\Logs" folder.

Launch a game, reproduce the bug then quit the game, open the lua.log with notepad and copy/paste everything in it in https://pastebin.com/ (or upload the files on a file hosting site like google drive) then post the generated link in a new thread with the description of the problem.

Sometime I may need some other file like the Database.log or the Modding.log to help finding the problem, I'll tell you if they are required.

Thanks.