Yes, as of September 14, 2017, POWr apps also work on the new Google Sites.
POWr also continues to work on the Classic Google Sites.
Up-to-date tutorials for how to add POWr apps, like Form Builder, Social Feed, PayPal Button, etc. to a Google Sites website are available in the "Add to Site" step of any POWr app.
Please note: Unfortunately, fixed positioned apps like Scroll To Top, Facebook Chat, Notification Bar, etc. do not work as intended on Google Sites. The platform is not set up to handle that type of install.