I recently upgraded to Scala 2.13.6 and I am seeing:
Error downloading org.scalameta:semanticdb-scalac_2.13.6:4.4.10
when I try to build.
I had a similar error when I upgraded to 2.13.5, but was able to add semanticdbVersion := "4.4.11"
to build.sbt to get it to work.
This is not working this time.
You can check on the central Maven repository which versions of the project is available for which version of Scala:
https://mvnrepository.com/artifact/org.scalameta/semanticdb-scalac
The only version built for Scala 2.13.6 is 4.4.18 as of today.
This info is probably also available on their GitHub release note oages