Problems with sbt-projectmatrix - upload artifact should be more granular

I am trying to port difflicious to use sbt-projectmatrix.

However the build fails at the uploadArtifacts stage:

Run tar cf targets.tar modules/weaver/target/jvm-2.13 modules/scalatest/target/jvm-2.13 modules/benchmarks/target/jvm-2.13 target docs/target/jvm-2.13 modules/core/target/jvm-3 modules/munit/target/jvm-3 modules/scalatest/target/jvm-3 modules/weaver/target/jvm-3 modules/benchmarks/target/jvm-3 modules/cats/target/jvm-3 modules/munit/target/jvm-2.13 modules/cats/target/jvm-2.13 modules/core/target/jvm-2.13 modules/coretest/target/jvm-3 modules/coretest/target/jvm-2.13 project/target
tar: modules/core/target/jvm-3: Cannot stat: No such file or directory
tar: modules/munit/target/jvm-3: Cannot stat: No such file or directory
tar: modules/scalatest/target/jvm-3: Cannot stat: No such file or directory
tar: modules/weaver/target/jvm-3: Cannot stat: No such file or directory
tar: modules/benchmarks/target/jvm-3: Cannot stat: No such file or directory
tar: modules/cats/target/jvm-3: Cannot stat: No such file or directory
tar: modules/coretest/target/jvm-3: Cannot stat: No such file or directory
tar: Exiting with failure status due to previous errors
Error: Process completed with exit code 2.

This is because directories for jvm-3 do not exist when we are building for jvm-2.13

Link to failed build

I saw https://github.com/sbt/sbt-github-actions/issues/9 but the mentioned workaround doesn't make sense in our case.

I guess this could be solved by overriding githubWorkflowGeneratedUploadSteps but the readme seems to discourage it and having a better support for sbt-projectmatrix seems like a good improvement.

Start by reading the generated upload steps, especially githubWorkflowGeneratedUploadSteps, and compare them with the sbt-projectmatrix build shown in the failed workflow. Done should be upload handling that does not fail when target directories for other JVM matrices are absent, while preserving artifact uploads for the directories that exist.