Hi Eliot, thank you for your advice.
I was able to solve the problem.
Based on the image of Companion 0.0.26, I modified the xml of /home/pi/companion/submodules/mavlink/message_definitions and issued the command of the companion setup script that I was taught.
After rebooting, I was able to confirm that the messages masked by Companion passed through Companion and reached from Pixhawk to the PC.
Please note that Pixhawk’s xml cannot be installed properly as it is, so I had to add only the points I wanted to change to the existing xml file.
Also, since I was taught the setup script, I tried to create the environment with the setup script, but I could not create it well due to bad timing. Therefore, try to prepare the environment based on 0.0.26.