First of all, thank you very much for this project!
Portmaster currently offers only stable installers. If you want to use a different channel, e.g. beta, it seems that the only way is to switch the channel in the UI and then let Portmaster itself handle the update.
I wonder if the offline installer could download either a specific version of Portmaster or use a specific update channel (stable/beta/etc.).
Is selecting a specific version or channel possible?