I got an answer from the support:
The S+RJ10 does not support forced link speeds and does not support speed advertisement configuration, it will always negotiate to the highest possible rate.
Unfortunately, it is not possible to change it
I got an answer from the support:
The S+RJ10 does not support forced link speeds and does not support speed advertisement configuration, it will always negotiate to the highest possible rate.
Unfortunately, it is not possible to change it