Basically everyone in the community agrees that Mint, Ubuntu and Fedora are the best choices for new users. Mint and Ubuntu are pretty similar, so they don't require separate maintenance effort, and supporting Fedora is not that hard, if you already support RHEL, CentOS or another rpm-based distro (which are pretty common in the enterprise space). For all the desktop applications, Flatpak exists and is agreed on as the standard format by most of the desktop Linux community.