It helps to identify the majority of problems in seconds. The file is found next to Cemu.exe. The file is proper after a game has run or crashed, not after you rerun Cemu because it gets recreated.
You can either
- Attach it with the "Manage Attachments" feature of a forum post, or
- Use pastebin or a similar service, e.g. https://pastebin.com/, or
- Simply copy and paste it in the post, preferably wrapped
PS. If your problem is too abstract in nature, it can be avoided but you may be surprised at how many times people think "I know my settings" or "I know my problem is too general" but their log.txt says otherwise.