I would always recommend checking the appropriate SCL (Software Compatibility List) for whichever version of Backup Exec you are planning to migrate to.
The SCLs for the different versions can be found here:https://www.veritas.com/content/support/en_US/article.100040087
Unfortunately CU17 for Exchange 2016 has only just been released in the last couple of months (June 2020) whereas BE15 is quite an old version of Backup Exec (base version over 5 years old, FP5 over 4 years old) consequently to get a version of BE that supports something as new as CU17, you would need to migrate to the latest release (v21.0) as even v20.6 only supports up to CU15.
@pkh Yes I'm aware it's not supported.
I was actually trying to restore individual items of Exchange 2016 that I've backed up to a B2D folder in BE15, but it only shows dataset when I tried restoring but no individual items.
Starting with Exchange 2016 CU5 the DB schema of Exchange was updated by Microsoft and older versions of BE like BE15 are not able to restore single items until you update BE to the latest version. Back then also other tools like Veeam was affected by this schema change.