@PhilipDAth and @BrechtSchamp are correct, and the official answer is no, there is no official 3rd party antenna support unless the antenna has been specifically certified, such as the Cisco Aironet AIR-ANT2513P4M-N on the Meraki MR84 for example. In that case that antenna is fully certified and supported.
That doesn't mean you cannot use 3rd party antennas, but it would be an unsupported configuration, and it is the customer's responsibility to understand and confirm you are within the maximum EIRP allowance within your regulatory domain. If you used 3rd party you could have to select the closest omni/patch/sector equivalent in Dashboard and perform an active post-deployment site survey. And if you called into Meraki Support asking them to troubleshoot RF issues, they may not be able to assist much with 3rd party antennas.