I did the same thing, and could not get my recovery sequence to work (like you above, tried MANY times and combinations). In the end, I loosely followed this post:
https://forum.xda-developers.com/t/mtcd-e-android-10-upgrade-using-official-free-tools.4123933/
What I did was use SDDiskTool to create a new SD card with an android 10 recovery image on it (option 1b on that post). I had to use the SD card as I could not get my usb to work when it was in android 11 / boot loop, even though it works at other times.
Firstly, as I have a PX6 unit, I downloaded: PX6_A10_IGV.img from
https://drive.google.com/drive/folders/11zpgoOW4eU6G1tjs7ExsZ2aC4RoZ9KDr
I had a lot of trouble with SDDiskTool version from that link (it just did not see my sd card). I found an older version of sddtool (v1.48 - just from googling). If you find it is in chinese writing, there is a config file just edit to change the language to 2. Then, start SDDiskTool and use it to write the PX6_A10_IGV.img to the SD card. When I pressed my reset button for around 12+ seconds, it would reboot, and with the SD card in the head unit, it installed an android 10 recovery prompt.
I then did a clear data / factory reset -- THIS IS IMPORTANT, I tried many times without this step and kept staying in the boot loop. At this stage with the android recovery menu up my usb was able to be used, so I just copied Hal's v5 to the usb key and chose the update option from the recovery boot. It then updated to the Hal9k mod (v5).
Good luck, I lost around 3 days to get this far, but I now have version 5.0.2 on my head unit and it all works. I can't get to version 5.1.0 but for now I am happy it is back to working for me.