Thermal flasher is still relevant technology, it works well even today. Electo-mechanical works via thermal mechanism

You need some kind of flasher, either use the stock thermal flasher or throw it away and fit an electronic flasher. Electronic type are needed for low-current LED flashers, the downside is they won't warn you if an indicator burns out. The good old thermal flasher slows down or stops blinking when one bulb is burned out, warning you to replace the bulb