As its name suggests, RGB-Pi OS/4 ALFa is still in development and may not be completely stable under all use cases, but the changelog is long enough to give it a try. As we can read in its wiki, the new version provides support for GunCon 2 pistols for all compatible systems (NES, SNES, arcade…), to which Dreamcast, Atomiswave, X68000 and DosboxPure are now added.
Another really big change is the addition of Dynares to the custom version of RetroArch that RGB-Pi OS uses. This software allows you to use the Raspberry Pi as if it were an “educated” graphics card with the Calamity drivers to provide 15-24-31 KHz progressive and interlaced, with the possibility of changing the resolution and the refresh rate within the game itself, all without tables timings external.
Finally, to everything listed (which is not little) new visual themes are added for the interface and backward compatibility with the official RGB-Pi hardware, such as its SCART cable and the JAMMA arcade adapter plate.
RGB-Pi OS/4 ALFa is now available for download, although it is important to point out that this version is not compatible with Raspberry Pi 3 and earlier models, since its developer has preferred to concentrate its efforts on the latest boards, which are considerably more powerful and capable. His official thread on EOL is here. Those who have an older Raspberry Pi and want to play games on a CRT TV can do so using alternatives like Retropie CRT Edition.