The file FDLAUNCHERRORLOG gets created in the default <instance>\MSSQL\Log folder.
So far, I've found absolutely no way to change that location. The link to a MS URL in a similar posted question here on SSC is Forbidden.
I asked our in-house AI, and it told me about the "SQL Server Fallback Database feature". I think it may have been hallucinating...
Any ideas?
Thanks!