Right-to-Left support for RibbonBar not currently in the schedule. Our focus is first to make the control a good solution for majority of the customers that go Left-to-Right. Then, depending on demand of RibbonBar from our customers that need Right-to-Left support, we will consider it for the roadmap. You can consider taking a look at third-party solution such as Ultimate Suite UI Controls to see if they support Right-to-Left today.
Our roadmap decisions are driven by customer demand rather then copying a particular 3rd party product. Also, certainly the first version of our Ribbon control is not going to match the third-party version developed for many years. Anyway, I'm sorry but adding RTL to the Ribbon control is not high priority so it is unrealistic to expect this in lets say 6 months. Why won't you just buy PBUS?
It looks to me like RibbonBar control in PB 2019 R2 does not have RTL support in the customer beta version. Also, I expect it for R2 final release. I expect more features like RTL and editor improvements will be added in later releases. The incremental approach of Appeon.
I like Appeon's approach of adding an MVP (min. viable product) edition of each new feature; then gradually extend that feature in later releases guided by customer feedback - like your question here, enhancement requests, and discussions at user groups and conferences.
Like NativePDF; extended in each release since PB 2017 GA. Like UI Themes; extended in R2. Like new WebBrowser in R2. Like C# Interop code generator in R2.