Mildly embarrassed thinking about how long I thrashed on this...
After creating a bee-u-tiful #eslint configuration, running it on my project, ensuring it hooked up to my editor etc.
Lint began failing when executed in CI. This left me so completely vexed that I dusted off my Fedora laptop to see if it was some arcane difference between MacOS and Linux.
It wasn't.
I realized that #rr7 needs to generate types before lint runs, or it rightfully explodes.
// package.json
{
...
"scripts": {
"check:lint": "react-router typegen && eslint .",
}
}