Thanks a lot for the advice, I tried it with unmounted cam, but still it didn't work. But finally I found out that I have to start the indiserver as superuser than the remote connection to the canon DSLR can be established.
I also tried to add a udev rule for the canon usb vids and pids, but even this doesn't work. So unfortunately have to accept to run the indiserver as superuser.

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