So, we just can party-hard to the 1st anniversary of this feature request in this new forum. To celebrate the day i´ve made a short video wich should show the dev´s what we mean and tickle their brains to implement this feature.
That said, head over to the technet (https://social.technet.microsoft.com/Forums/en-US/01cd6768-fcaf-4f2b-a726-491e1aa702e7/is-fullscreen-support-on-the-11-ipad-pro-too-much-to-ask-for?forum=winRDc) where this request was answered with "I will post your suggestion/feedback to product team." In 02/2019. This suggestion is really a killer I think. Additional found via WBM the original suggestion in the uservoice board - with 154 upvotes and status "planned" (https://web.archive.org/web/20200928092906/https://remotedesktop.uservoice.com/forums/925639-remote-desktop-beta-client-for-ios)
Really MS this shame on you. https://youtu.be/kbAVH0m7WAk
The app i used is called https://www.jumpdesktop.com/ . But its 19,99 Eur each license. But JD just not support RD-Gatway connection. They deev´s should meet each other, just an idea 😄