If you want to use the built-in Canon RT radio system, then you need a unit that speaks the Canon RT radio protocol.
The only gear, aside from Canon's ST-E3-RT, 600EX-RT, and 430EX III-RT that does so, are clone units from Yongnuo, Shanny, and Phottix. Yongnuo have clones of the 600EX-RT and ST-E3-RT, and both are compatible with Canon's gear, but have slightly different feature sets. Shanny and Phottix at this time only have ST-E3-RT clones, the SN-E3-RT and Laso transmitter, respectively.
In addition, Yongnuo has also released the YNE3-RX receiver and Phottix has released the Laso TTL receiver that can be used with eTTL-compatible flashes. These units handle the ID codes and groups, and provide eTTL, and HSS. Early reports also say that the YNE3-RX supports Gr mode group control, Supersync (aka tail sync, HyperSync), and 2nd curtain sync like the YN-622 triggers. The Laso features are not yet well known, but they do not do 2nd curtain sync.
If you are new to Yongnuo gear, do some research, and learn about how to read manufacture date codes, and who the reputable retailers are with good return policies. I'd say keep an eye out on the Flash Havoc blog, and the POTN messageboard's thread on the YNE3-RX. Phottix's reputation is a bit better than Yongnuo's in terms of reliability and build quality, but they have pricetags to match.