So, did as you suggested - LineageOS first

Well at first tried the stock. As for me it is mainly a device with physical keyboard, then paid most attention to keyboard use. Unfortunately the qwertz version is not still fully supported. I mean these yellow arrow&characters. Did not find a way to type an õ character. Unfortunately in estonian it is widely used - an example: "õlu" is beer in estonian This reminds me my N900 where I had zero problems with german layout and estonian letters...

LineageOS - installation was successfull, but again the german qwertz keyboard use is not still there. It seems that the developer is aware of the problem and it is in his todo list.

SailfishOS - the suggested installation procedure did not work. Was able to flash TWRP, but that did not start - only until splashscreen and got stuck there. Tried to sideload SailfishOS with Lineage recovery but that did not succeed.

The hardware seems to be good or at least satisfactory. Yes, the screen rattles a little. And my Nexus 6 seems to have better screen and camera...

So - back to be box and drawer for now. Or should I put it on sale?