I would like to detect what version of SQL Server Express engine is available so that I can connect either to the (localdb)\v.11 (SQL Server 2012 per https://learn.microsoft.com/en-us/previous-versions/sql/sql-server-2012/hh510202(v=sql.110)?redirectedfrom=MSDN#Anchor_1) or (localdb)\MSSQLLocalDB (SQL Server 2014 and up per https://learn.microsoft.com/en-us/sql/database-engine/configure-windows/sql-server-express-localdb?view=sql-server-ver15&redirectedfrom=MSDN&viewFallbackFrom=sql-server-2014#Anchor_1) instance name when attempting to attach a file in the connection string using the AttachDBFileName= mechanism.
I would most likely want to do it from Powershell in some manner, but whatever method is reliable, I can use. I do know that sometimes a LocalDB connection can be a bit slow as it attaches the file and starts up on demand, so I have in the past been pretty lenient on the connect timeout for these LocalDB connections compared to the real SQL Server connections, so I would prefer not trying to connect and waiting for timeout, since I think I've already got an exaggerated timeout just for normal successful connection.