I should also note (in case somebody else has the same problem) that somewhere in the process, my app.json file was changed into this:
{
"name": "AppName",
"displayName": "AppName",
}
But to successfully run expo start
it needs to be this:
{
"name": "AppName",
"displayName": "AppName",
"expo": {
"sdkVersion": "30.0.0"
}
}