I have this problem with k3b in 18.04 releases (Ubuntu, Kubuntu, KDE Neon...) In oldest releases I do not have this problem:
cdrecord has no permission to open the device
You may use K3bbsetup to solve this problem.
I've searched online but I have not found any solution.
Can anybody help me?
Try attempting the following commands:
This will set the UID bit on the necessary binaries. It is illustrated in Settings -> Configure k3b -> programs -> Permissions "tab".