It's now (once again) super easy to try the latest Plone version on a free Heroku account.
Hmm... the Mosaic that it ships with needs an upgrade.
@pigeonflight I'll be happy to update the pins and test that it works, if someone can provide me with the latest ones that work, that I can just slot in. I don't work on Mosaic myself much, otherwise I'd do it myself. Thanks!
Here's a pull request https://github.com/collective/training-sandbox/pull/12
Tested to be working. Merged.