You are welcome, Tealer!
You said: ‘ Phala-sammāpatti I understand as saññā vedayita nirodha.”
- saññā vedayita nirodha is the phala samapatti corresponding to the Arahant phala.
- Phala samapatti for lower stages of Nibbana are different. For example, a Sotapanna could cultivate Sotapanna phala samapatti.
You wrote: “For my understanding, Magga and phala itself (and the phala-sammāpatti even more) is a special kind of jhanic experience.”
As explained in the post, “Pannāvimutti – Arahanthood without Jhāna“, one could get to magga and phala without going through jhana.
You wrote: “So even the paññāvimutti Arahat must have at least some jhanic moments.”
It is possible that a paññāvimutti Arahant may automatically get to the first Ariya jhana. I am not certain about that. Of course, he/she would be easily able to cultivate jhanas after the Arahanthood.
– However, the Abhidhamma description of any magga phala involves only a gotrabu (change of lineage) citta; see at the end of the following post for a a short description: “Citta Vithi – Processing of Sense Inputs“.
You asked: “do you think that every ubhatobhāga-vimutta must be (beside paññāvimutta) also akuppā cetovimutta?”
Ubhatobhāga Arahant means one who is liberated “both ways”.
– a cetovimutti ARAHANT is, by definition, an Ubhatobhāga Arahant.
– a paññāvimutti Arahant can become an Ubhatobhāga Arahant by cultivating jhana and getting to saññā vedayita nirodha.
You may be also interested in the post, “Jhānic Experience in Detail – Sāmaññaphala Sutta (DN 2)“, which was published today.