G960F_ZTA2_ZTA9 (S9) (Beta 6) (Exynos): http://fota-secure-dn.ospserver.net/firmware/BTU/SM-G960F/nspx/506e5820a2bc4035b95d20f9869aef13.bin?px-time=5e6c8729&px-hash=624d2943cf0f54def8650ec21f45b87a
Aah, looks like hochocnua is faster.
Galaxy S9 (ZSL2 to ZSL9): http://fota-secure-dn.ospserver.net/firmware/BTU/SM-G960F/nspx/8cd449bf8dd1460d8968ab6354365988.bin?px-time=5e4a8608&px-hash=5ca8f3ce046a130be9a7ef07f44b3421
Via floxay: https://forum.xda-developers.com/showpost.php?p=81245331
16.2017.1912.072 is live, should bring December security patch.
Full zip: https://dlcdnets.asus.com/pub/ASUS/ZenFone/ZB631KL/UL-ASUS_X01BD-WW-16.2017.1912.072-user.zip
Guess you don't made any mods, such as Magisk patched boot image? Is the bootloader unlocked? Can you please post a screenshot?
On the other hand, you can downgrade using the full zip of Pie build. However, the data (including internal storage) will be wiped.
Technically yes, as the new build (V10.0.15.0.PDLMIXM) is live on Xiaomi update servers.
16.1220.1909.194 is live: https://zentalk.asus.com/en/discussion/11214/190928-zenfone-6-zs630kl-ww-16-1220-1909-194
Full zip: https://dlcdnets.asus.com/pub/ASUS/ZenFone/ZS630KL/UL-ASUS_I01WD-ASUS-16.1220.1909.194-1.1.1-user.zip
Like previous generations, the MIUI counterpart (in this case, Mi CC9e) has legacy A-only partitioning scheme whereas the Android One variant has A/B one. Frankenbuilding should be possible, but complete conversion is a complicated job.
June 2019 (V10.0.10.0.PDHMIXM) full OTA zip: http://bigota.d.miui.com/V10.0.10.0.PDHMIXM/miui_TISSOT_V10.0.10.0.PDHMIXM_09627ae708_9.0.zip
As _mysiak_ mentioned, this is the full signed zip intended to flash via recovery. However, Xiaomi's stock recovery can't be used.