Step 4 fails w/ invalid fragment object

[jsoares]

Context: Trying out the trampoline from the start, running Ubuntu 22.04 & nodejs 20, modified package.json to use ethers 5.x (see #5), and having run npm install on the repo.

Runs through the various web UI steps with no issue. On getting to Step 4 "Create Subnet", I get this error:

Nothing useful in the logs.