I did say that the RX500 can use pigment ink in my assessment of the RX500.
It is better to get a set of refillable cartridges and use those for pigment ink printing rather than trying to convert the original cartridges. With the pigment ink, it is advisable to get a custom profile with the paper you intend to use as the colors won't be as accurate as the standard Epson cartridges which the printer was designed for. The issue with converting the original involves emptying the original of the dyebase ink completely which is not a simple thing given the internal complexity of the channels. Become familiar and familiar with all aspects of the machine before undertaking the conversion or adaptation to pigment ink.
It is better to get a set of refillable cartridges and use those for pigment ink printing rather than trying to convert the original cartridges. With the pigment ink, it is advisable to get a custom profile with the paper you intend to use as the colors won't be as accurate as the standard Epson cartridges which the printer was designed for. The issue with converting the original involves emptying the original of the dyebase ink completely which is not a simple thing given the internal complexity of the channels. Become familiar and familiar with all aspects of the machine before undertaking the conversion or adaptation to pigment ink.