Playing on a CRT television means getting the exact picture of the era back: original resolutions and refresh rates, phosphors, natural scanlines. Recalbox is one of the few systems producing a true native 15 kHz RGB signal, and that support is built into every Raspberry Pi image (Zero 2, 3, 4/400, 5/500).
For the list of supported screens and the other video outputs, see Screens. To tune Kodi on a CRT, see Optimizing the Kodi display for CRT.
Need help? Join the Recalbox Discord, the CRT channel is very active there.