Thanks @piero for this hint.
So according to your guide, it looks like this:
Android 13
- What is the latest available StockOS android version but not higher regarding to the android version of the /e/OS build you want to install ?
Android 15
Or what is the precise StockOS version required as a base to install the /e/OS build you want to install
Android 14
- If answers to 1 and 2 are the same, you can have a go for dirty upgrade !
- If answers to 1 and 2 are differents, you must answer to questions 3 or 4
- does latest /e/ build include the upgraded needed parts of the firmware ?
download it and have a look inside the .ZIP (you may need to extract it)
what to do if you find a payload.bin file ?
Yes - playload.bin is there - does Lineage wiki offer a firmware upgrade solution for this device ?
No - as far as I can see
- if answers to 3 and 4 are no, you will have to install latest available full Stock OS (relative to the android version of the /e/ build you want to install → not higher), then reinstall /e/OS from scratch.
- if answer to 3 is yes, you can have a go to dirty upgrade /e/OS.
- if answer to 4 is yes, you can have a go for dirty upgrade the firmware, then dirty upgrade /e/OS !
So, in my case: There is no (?) possibility to upgrade A13 to A14, right.
Means, I can’t do the dirty upgrade to e/OS 3.3
Means, I have to do the factory reset again?
Or did I get it wrong?