Semantic Modeling Language (SMDL)
SQL Server 2016+
SMDL models were deprecated as of the release of SQL Server 2014, the ability for them to function was still there. SSRS 2016 or later doesn’t support the Report Models feature.
Uploading and managing report models is a discontinued feature on SQL Server 2016 (is no longer a deprecated feature) and the workaround is explained on the following article:
You should try to update reports and remove dependencies on report models.