.NET 6 Linux multicontainer app not cannot establish container inter-communication in Azure App Service

I cannot for the life of me get my Azure App Service multicontainer app with 3 containers working, where they can communicate with each other. I've tried for the better part of a week without any luck...

It's a .NET 6 app written in C# with 3 containers deployed - a web app, a Redis server and a MSSQL server - using Docker Compose and Azure DevOps. Deployment works as expected, but the web app fails because it cannot establish a connection to either the Redis server (using port 6379) or the MSSQL server (using port 1433)

The Docker Compose file looks something like this:

services:
  website:
    image: <registryname>.azurecr.io/<containername>:latest
    container_name: web
    restart: always
    build:
      context: .
      dockerfile: Presentation/<WebProject>/Dockerfile
    environment:
      - ASPNETCORE_ENVIRONMENT=Production
  db:
    image: mcr.microsoft.com/mssql/server:2019-latest
    container_name: db
    ports:
      - "1433:1433"
    volumes:
      - mssql:/var/opt/mssql/data
    environment:
      SA_PASSWORD: "<password>"
      ACCEPT_EULA: "Y"
  redis:
    image: <registryname>.azurecr.io/redis:7.0.4
    command: redis-server --requirepass <redisPassword>
    ports:
     - "6379:6379"
    volumes:
     -  redis_data:/var/lib/redis
    environment:
     - REDIS_REPLICATION_MODE=master

volumes:
  mssql:
    external: true
  redis_data:
    driver: local

And the deployment YAML file looks something like this:

trigger:
  branches:
   include:
     - 'master'
  paths:
   include:
     - Presentation/<WebProject>/*
   exclude:
     - Presentation/<ApiProject>/*

resources:
- repo: self

variables:
  # Container registry service connection established during pipeline creation
  azureContainerRegistry: '{"loginServer": "<registryname>.azurecr.io", "id": "/subscriptions/<subscription-id>/resourcegroups/<resourcegroup>/providers/Microsoft.ContainerRegistry/registries/<registryname>"}'
  azureSubscription: '<Name of service connection to Azure Resource Manager>'
  appName: <Azure app service app name>
  imageRepository: '<image name in registry>'
  containerRegistry: '<regsitryname>.azurecr.io'
  tag: latest

  # Agent VM image name
  vmImageName: 'ubuntu-latest'

stages:
- stage: Build
  displayName: Build and push stage
  jobs:
  - job: Build
    displayName: Build
    pool:
      vmImage: $(vmImageName)
    steps:
    - task: DockerCompose@0
      displayName: 'Build images'
      inputs:
        containerregistrytype: Azure Container Registry
        azureContainerRegistry: $(azureContainerRegistry)
        azureSubscription: $(azureSubscription)
        dockerComposeFile: 'docker-compose-web-azure.yml'
        action: Build services
        arguments: website
    - task: DockerCompose@0
      displayName: 'Push images'
      inputs:
        containerregistrytype: Azure Container Registry
        azureContainerRegistry: $(azureContainerRegistry)
        azureSubscription: $(azureSubscription)
        dockerComposeFile: 'docker-compose-web-azure.yml'
        action: Push services
        includeSourceTags: true
        includeLatestTag: false
    - task: AzureWebAppContainer@1
      displayName: 'Azure Web App on Container Deploy'
      inputs:
        azureSubscription: $(azureSubscription)
        appName: $(appName)
        imageName: $(containerRegistry)/$(imageRepository):$(tag)
        multicontainerConfigFile: 'docker-compose-web-azure.yml'

All containers starts up as expected with no errors in the logs.

I've modified my Dockerfile for the web project so that I can SSH into the container from Azure App Service and test connectivity to other containers using telnet. Example:

telnet localhost 1433
telnet 127.0.0.1 1433

And a bunch of other stuff. Nothing works.

Am I better off using an Azure VM (where I can at least control everything, including Docker networks which I use on my own machine), or is there a solution to this?