The flatpak has been working for me on Linux Mint, although the flatpak didn’t work on Ubuntu proper. From what I understand the Mint devs do some extra tinkering to support flatpaks better than vanilla Ubuntu. Have you tried downloading the binary and running it from a terminal?
The Appimage also works well for me on my Ubuntu XFCE box.
The flatpak has been working for me on Linux Mint, although the flatpak didn’t work on Ubuntu proper. From what I understand the Mint devs do some extra tinkering to support flatpaks better than vanilla Ubuntu. Have you tried downloading the binary and running it from a terminal?
The Appimage also works well for me on my Ubuntu XFCE box.
https://www.openra.net/download/#linux