The TP-Link Archer AX50 would be a good router to use with your Deco X20 mesh system. It's a high-performance Wi-Fi 6 router that would complement the capabilities of your Deco X20 mesh system well.

Another option is the TP-Link Archer C4000. This is a tri-band router that supports both Wi-Fi 5 and Wi-Fi 6 devices. It also has a high-speed Ethernet backbone that can support multiple Deco X20 units in a mesh configuration.

Both of these routers are compatible with your Deco X20 mesh system, and they can be used in conjunction with it to provide additional Wi-Fi coverage and capacity. It's worth noting that you don't need to replace your Deco X20 units to use OneMesh, as it's a feature that can be enabled on existing Deco devices via a firmware update.

  @TheTrexpot Thank you for the response about the two potential routers to replace my ISP router.

Could you explain more about this comment "It's worth noting that you don't need to replace your Deco X20 units to use OneMesh, as it's a feature that can be enabled on existing Deco devices via a firmware update." I had not seen any information about this, maybe you have a pointer to some docs that explain this and I can easily update the firmware.