I couldn't get heroku:24 to work, but I was able to build .NET 10 with
pack build $CONTAINER --buildpack paketo-buildpacks/dotnet-core --builder docker.io/paketobuildpacks/ubuntu-noble-builder-buildpackless --env BP_DOTNET_PROJECT_PATH=./$TARGET
where $CONTAINER is the name of my container and $TARGET the directory it is in