net9 not available on focal (but supported, according to MS?)
diff --git a/build/docker/ubuntu-focal/Dockerfile b/build/docker/ubuntu-focal/Dockerfile
index 52ea5a4..831d07e 100644
--- a/build/docker/ubuntu-focal/Dockerfile
+++ b/build/docker/ubuntu-focal/Dockerfile
@@ -139,10 +139,10 @@
RUN apt-get install -y --no-install-recommends \
`# dotnet core dependencies` \
- dotnet-sdk-9.0 \
- dotnet-runtime-9.0 \
- aspnetcore-runtime-9.0 \
- dotnet-apphost-pack-9.0
+ dotnet-sdk-8.0 \
+ dotnet-runtime-8.0 \
+ aspnetcore-runtime-8.0 \
+ dotnet-apphost-pack-8.0
# Erlang dependencies
ARG ERLANG_OTP_VERSION=23.3.4.11