[Smush Pro] Issues with Smush & caching

Hi wpmudev team,
I recently bought a wpmudev licence (with a nice Blackfriday discount, thank you for that!) and started implementing the plugins.
Smush Pro was first on my list, as I was a Smush user already (free version). I was aiming for better jpg/png compression, combined with using your CDN. Installation, bulk smush, map smush, CDN… It all went fine.
Then I installed Hummingbird and ran a performance test. The “Audits” section of the Performance test recommends to “Serve images in next-gen formats”, followed by a list of images in the upload folder (that are effectively used on my site). I should use Smush Pro to fix this…
Also, I should “Efficiently encode images”, using Smush Pro… and “Avoid enormous network payloads” (the same pictures are listed because of not being Smush’ed I assume).

Smush settings: All image sizes, Automatic compression on, Super-Smush on, remove metadata, PNG to JPG conversion, Bulk Smush successfully done. No Lazy Load because of documented issues with Uncode Adaptive Images feature.

I use WP 5.3, Uncode theme v2.2.3 (with child theme active), PHP 7.2.18, running on Apache/2, url https://www.monx.be
I successfully ported my site to wpmudev.host to see if I’d run into the same issues, and that is indeed the case, url http://www.wpmudev.host (password protected for the moment)

I could really use some assistance/support here, as I’m looking for a solution for days now.