Hi,
at first big thx to @MrT10001 and his hint regarding oxygenOS. After some trial and error, everything went smoothly through EBL Mode and MSM Tool. Unfortunately my old Thinkpad now runs on Windows 10 but thats ok
Second, coming from Ubuntu touch on a Oneplus 3 where video recording never worked... now on OP N10, a dream! I´m so happy!
So far so good, thanks for the quick help. Looking forward to deep-dive into maybe daily-driving my new device some day.
@DJac I think thats not the correct build/version, my phone is billie not aviici.