Single user mode when was configured I'm trying to find when a database on our instance was configured as SINGLE USER MODE but can't find that information. Either using tsql or the GUI. Maybe it is not possible to know that information? Are these actions logged somewhere? Or do we need to force this logs?
Maybe it is not possible to know that information?


Exactly. It is assumed to be non-critical. You may (should) be lucky with the sql server logs but then those rorate and it is quite likely to no there - anymore (unless it happened very recently).

Check the SQL Server logs , imho your best chance.