So a few comments...
- I'm not a fan of Ubuntu server, in part because their distribution of docker through snap can conflict with snap from the docker repo. My preference here is either Debian or Proxmox (debian + great virtualization setup). Mint is good, though I like LMDE (Debian edition) more, in part because I prefer Debian in general.
- You may want to check out dockge. You do need to have docker running for it, but it's a simple setup, and it has a clean interface for docker compose. Good for getting used to it imo.
- grub has no part in docker, so it's something else hanging.
- What are the exact errors when you enter "docker-compose up"?
- what is in your docker-compose for each of these?
I like this a lot more vertically!
I also think it could have a bit less detail and get the point across, which would let it scale better.