Following issues on imports seem to be connected to #3004:

// src/index.jsx

// Fails (when cache is clean):
import Avatar from '@material-ui/core/Avatar';
import Alert from '@material-ui/lab/Alert';

// Works: also caches other components which makes the previous imports not fail
import { Avatar } from '@material-ui/core';
import { Alert } from '@material-ui/lab';

// ^ Both seem to work on build (when there's no alias defined in snowpack.config.js)

Also when running snowpack build with the following config, it finishes succesfully but the build fails on the browser:

// snowpack.config.js
{
  alias: {
    // these seem to work fine in snowpack dev but not when making a build:
    '@material-ui/core/Avatar': '@material-ui/core/esm/Avatar',
    '@material-ui/lab/Alert': '@material-ui/lab/esm/Alert',
  }
}

For this last part, in medium-big sized projects changing every Material UI import from import Avatar from '@material-ui/core/Avatar' to import { Avatar } from '@material-ui/core' might be hard and take too long so I thought creating an alias in snowpack.config.js would make it easier without changing all of the imports.