Thanks for your suggestion. I can run latest Sailfish on LOS 14.1. - and it is absolutely great (I use it as my daily driver)
I was just wondering if anyone else experienced similar issue to mine (I could see a guy's case with exactly the same problem in couple of posts earlier).
But anyway, you've previously mentioned there is no big difference between running sailfish on base 14.1 vs 15.1 so I will stick to 14.1. - I am sure that I am doing something wrong when I try to install LOS 15.1 so gonna find it out somehow.
Edit1: Can a newer vince firmware than suggested one (fw_vince_miui_HM5PlusGlobal_8.11.15_dd40bfa136_8.1.zip) be flashed? Or this firmware version is mandatory in order to run sailfish ? I just read in different forum thread that it solved the vendor image mismatch issue for a guy.
Edit2:By reading previous posts within this thread I see there are many others who have the same installation issue with flashing latest sailfish over LOS base 15.1. If someone found the solution please share it here as I am still investigating about it.