Is your feature request related to a problem? Please describe.

I noticed a user to specify cfg.channels rather than cfg.channel, where the channel selection was subsequently ignored. This lead to unexpected results further down in the analysis.

Describe the solution you'd like

Using ft_checkconfig we could make cfg.channels forbidden in all high-level functions.

Describe alternatives you've considered

We could also make use the ft_checkconfig renamed option and rename channels into channel. Since channels was never used, I am not in favor of that.