Dev Container error ERR_EMPTY_RESPONSE on M1 mac

Hi, trying to add an integration from my M1 mac.
I followed the “set up development environment instructions” to a tee, twice, but using my browser and hitting http://localhost:8123/ returns:

localhost didn’t send any data.

ERR_EMPTY_RESPONSE

I am on an M1 mac, latest fork checked out and rebased against upstream, updated docker and vscode. In vscode, the Ports section lists 8123 as statically mapped, and 36323 as auto forwarded.

the last lines from my vscode terminal are:

Requirement already satisfied: h11<0.15,>=0.13 in /usr/local/lib/python3.10/site-packages (from httpcore<0.18.0,>=0.15.0->httpx>=0.21.0->respx==0.20.1->-r requirements_test.txt (line 33)) (0.14.0)
Installing collected packages: pre-commit
  Attempting uninstall: pre-commit
    Found existing installation: pre-commit 3.3.1
    Uninstalling pre-commit-3.3.1:
      Successfully uninstalled pre-commit-3.3.1
Successfully installed pre-commit-3.1.0

[notice] A new release of pip is available: 23.0.1 -> 23.1.2
[notice] To update, run: pip install --upgrade pip
Done. Press any key to close the terminal.

What am I doing wrong? Or is the dev container broken for M1s ?