In 1.5 album versions are sorted according to quality. Since your ALAC and FLAC are identical I assume ALAC is displayed first because A comes before F.
Since both are lossless formats and one was derived from the other I don’t understand why you’d want to keep both in your library. However, you could hide all of the ALAC albums as suggested by @Dick_Vliek. Otherwise, you’d need to go through each version and select Make Primary Version for FLAC.
That’d be my suggestion too. Use Focus to identify FLAC, then Inspector > Duplicates, and finally click on +FLAC to identify the ALAC files that have alternative versions. Now follow previous instructions to hide these.
I can’t explain why but playing the same track in alac and flac through Roon sounds not the same. The Alac version is slightly more dull but easier to listen to compared with flac, more open - sounds like it comes with a hint of what I would call “digitalize”.
Both played through SB Touch and strait to my amp. Maybe something to do with the D/A conversion in the SB maybe?
Therefore, I keep both versions also in case I should end up with Itunes one day again.
To support what @Martin_Webster says, in the Roon architecture both FLAC and ALAC are decoded in the Core server, and if they are exact copies they send the exact same datastream in the same format to the endpoint. No difference to the DAC.
If you keep hearing such differences you might want t9 find out if the files are not exact copies.