I successfully installed RStudio from the flatpak Alexander Wilms kindly provided, but the link in his posting What about R in endless appears to be defunct. I hope I still have the flatpak on my Endless Acer, but I also don’t know wehere I could put it.
I still do not understand how flathub handles build processes. I assumed that it builds flatpaks aautomagically if somebody provides the manifest. And in my understanding Alexander Wilms has provided the manifest, so there should be some RStudio flatpak on flathub, which I cannot find, but I might be missing the point. Also I did not succeed in building a RStudio flatpak with the manifest of Alexander Wilms provided here: https://github.com/Alexander-Wilms/flathub/tree/rstudio but maybe someone with a better understanding of flathub/flatpak build process could help.