Trackers like U360GTS cannot work with Mavlink2 correctly and do have a problem with unfiltered high bandwidth Mavlink streams.
I wrote a small filter utility https://github.com/fingadar/trackermavfilter . It takes a Mavlink2 stream from UDP or STDIN (for OpenHD i.e.) and outputs only the tracker relevant Mavlink messages as Mavlink1 to an UART. It outputs only Mavlink messages MAVLINK_MSG_ID_GLOBAL_POSITION_INT, MAVLINK_MSG_ID_GPS_RAW_INT, MAVLINK_MSG_ID_ATTITUDE to an uart to reduce data traffic.
A possibility to include it in OpenHD would be
cat /var/run/openhd/telemetryfifo6 | /home/pi/trackermavfilter/trackermavlinkfilter -d /dev/ttyUSB0 -b 115200 -n
(or the use of the corresponding params from the openhd-settings-?.txt config)
I would be happy if someone could get some benefit from it. If you have any questions, feel free to ask