I confirm it works for me, side by side FR24 and the open sky feeder with:
* rename of the "/usr/bin/openskyd-dump1090" to " /usr/bin/openskyd"
* rename of the service binary from " /lib/systemd/system/opensky-feeder.service" to use " /usr/bin/openskyd"
* add procargs="--net" to /etc/fr24feed.ini
I have added the APT repository, so I suspect the next update will break the renaming, and I will have to apply it again.
Would be nice if open network would rename the service name at source?