Localstack returning error when trying to provision a dotnet8 lambda

I'm trying to provision a lambda on a free localstack instance. As such, I cannot build the lambda as an image and push it into localstack's ECR because ECR is a paid resource. So I'm taking the approach of using "sam" and having that do all the heavy lifting for me.

My docker-compose is running:

  my-service-localstack:
    container_name: my-service-localstack
    build:
      context: .
      dockerfile: localstack/Dockerfile
    ports:
      - 4576:4566
    networks:
      - blah
    environment:
      - AWS_DEFAULT_REGION=us-east-1
      - AWS_ACCESS_KEY_ID=test
      - AWS_SECRET_ACCESS_KEY=test
      - LAMBDA_EXECUTOR=local
      - LAMBDA_DOCKER_NETWORK=blah
      - DOCKER_HOST=unix:///var/run/docker.sock
    volumes:
      - ./localstack/init-localstack.sh:/etc/localstack/init/ready.d/init-localstack.sh
      - ./localstack/template.localstack.yml:/var/lib/localstack/template.localstack.yml
      - ./src/AWS.Lambdas/ConfigAggregator-lambda/src:/src/AWS.Lambdas/ConfigAggregator-lambda/src
      - /var/run/docker.sock:/var/run/docker.sock

That runs my Dockerfile which installs the .Net 8 SDK into the latest localstack image as well as the sam-cli and awscli.

# Start from the official LocalStack image
FROM localstack/localstack:latest

# Install AWS SAM CLI and awscli-local
RUN pip install --no-cache-dir aws-sam-cli awscli-local

# Install .NET SDK (example for .NET 8)
RUN apt-get update && \
    apt-get install -y wget apt-transport-https && \
    wget https://packages.microsoft.com/config/debian/12/packages-microsoft-prod.deb -O packages-microsoft-prod.deb && \
    dpkg -i packages-microsoft-prod.deb && \
    apt-get update && \
    apt-get install -y dotnet-sdk-8.0 && \
    rm -rf /var/lib/apt/lists/*

ENV PATH="$PATH:/root/.dotnet/tools"

Next we have the localstack startup script which runs as the container is starting up since we copied it into the container in our docker compose:

#!/bin/bash
set -euxo pipefail
set -e

# Point AWS CLI calls to LocalStack
export AWS_ACCESS_KEY_ID=test
export AWS_SECRET_ACCESS_KEY=test
export AWS_DEFAULT_REGION=us-east-1
export AWS_ENDPOINT_URL=http://localhost:4566

# Build the Lambda image from your Dockerfile
sam build --template /var/lib/localstack/template.localstack.yml

# Deploy into LocalStack, pushing the image into LocalStack's ECR
sam deploy \
  --stack-name my-service\
  --resolve-s3 \
  --region us-east-1 \
  --capabilities CAPABILITY_IAM \
  --no-confirm-changeset \
  --no-fail-on-empty-changeset

Finally, we provision our localstack resources themselves in a cloud formation template that we told sam above to build:

---
AWSTemplateFormatVersion: 2010-09-09

Transform:
  - AWS::Serverless-2016-10-31

Description: >
  Creates/Manages an my-service stack

Metadata:
  cfn-lint:
    config:
      ignore_checks:
        - W3002
        - I3042
        
Parameters:
  S3ConfigBucketName:
    Type: String
    Default: 'my-service-config-aggregator'

Resources:
  ConfigAggregatorBucket:
    Type: AWS::S3::Bucket
    DependsOn:
      - ConfigAggregatorLambda
      - ConfigAggregatorLambdaPermission
    DeletionPolicy: Retain
    UpdateReplacePolicy: Retain
    Properties:
      BucketName: !Ref S3ConfigBucketName
      NotificationConfiguration:
        LambdaConfigurations:
          - Event: s3:ObjectCreated:Put
            Function: !GetAtt ConfigAggregatorLambda.Arn

  ConfigAggregatorLambda:
    Type: AWS::Serverless::Function
    Properties:
      FunctionName: ConfigAggregator-lambda
      Runtime: dotnet8
      Handler: ConfigAggregator_lambda::ConfigAggregator_lambda.Function::FunctionHandler
      CodeUri: /src/AWS.Lambdas/ConfigAggregator-lambda/src
      MemorySize: 512
      Timeout: 30
      Environment:
        Variables:
          REFRESH_FUNCTION_NAME: ''
          CONFIG_BUCKET_NAME: !Ref S3ConfigBucketName
          
  ConfigAggregatorLambdaPermission:
    Type: AWS::Lambda::Permission
    DependsOn:
      - ConfigAggregatorBucket
      - ConfigAggregatorLambda
    Properties:
      FunctionName: !Ref ConfigAggregatorLambda
      Action: lambda:InvokeFunction
      Principal: s3.amazonaws.com
      SourceArn: !GetAtt ConfigAggregatorBucket.Arn

All of that executes fine, but when the resources go to provision, I get the following error in my localstack container in Docker Desktop:

CREATE_FAILED AWS::Lambda::Function ConfigAggregatorLambda An error occurred (InvalidParameterValueException) when calling the CreateFunction operation: Value dotnet8 at 'runtime' failed to satisfy constraint: Member must satisfy enum value set: [java17, provided, nodejs16.x, nodejs14.x, ruby2.7, python3.10, java11, python3.11, dotnet6, go1.x, nodejs18.x, provided.al2, java8, java8.al2, ruby3.2, python3.7, python3.8, python3.9] or be a valid ARN

Looking at localstack's documentation: https://docs.localstack.cloud/aws/services/lambda/#special-tools

They note that they:

matching AWS parity (i.e., excluding deprecated runtimes)

AWS supports: https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html#runtimes-supported

Note that dotnet6 is deprecated and dotnet8 is supported.

Any ideas where the disconnect is? I can't seem to find much information on which runtimes localstack supports in the free account but I can see that they added official support for dotnet8 here: https://github.com/localstack/localstack/pull/10300

Any advice is appreciated.