I have a HK1 Rbox with Amlogic s905x4 2Gb Ram 100Mb Lan. There is no sound via HDMI on the very first boot after turning everything on, after rebooting again everything works fine (rebooting kodi doesn’t help). I think it is a similar issue as described above, if the box starts before my AVR fully on and running (but I don’t have any display issues, I guess because AVR powers on faster than a TV. But if the box turned on with AVR powered off, I do see a colour box like on the screenshot above instead of image).
I’ve captured the content of dmesg and kodi log, when there is no sound and when there is sound. And one more thing - Corelec 20.1 NG doesn’t seem to be affected, I tried it a couple of times but will do more testing today, seem like a NE issue.
dmesg no sound
kodi.log no sound
can’t put more than 2 links in a post, so
dmesg with sound
kodi.log with sound
P. S. Wifi doesn’t work in NE either, but it does work in NG. I don’t really care, just FYI
No 23.976 (23.98) Hz on TV with CE ne 20.,20.1, nightly. CE ne just switch to 24 HZ (always, with or without whitelist in system setting). Vontar X4, gbit. In CE ng its ok with X96m+ (X3). My LG tv can detect 23.98 and 24 Hz.
No 23.976 (23.98) Hz on TV with CE ne 20.,20.1, nightly. CE ne just switch to 24 HZ (always, with or without whitelist in system setting). Vontar X4, gbit. In CE ng its ok with X96m+ (X3). My LG tv can detect 23.98 and 24 Hz.
All info is from latest nightly CE ne.
In whitelist is all enabled:
TV info:
LOG:
http://ix.io/4sMv
The same video with X3 box is correct 23.98 Hz:
TV info:
frac 1 means: 24 / 1000 * 1001 = 23.98Hz
Thx. But why by tv is detected 24 Hz? In debug are skipped frames (about 6 per minute) . In X3 (CE 19.5, 20 ng) skip is 0.
In Slimbox Vontar X4 its ok, 23.98 Hz, no skip. Same video. So its not hw problem.
Log from X3 box (X96m+) . CE 19.5.
http://ix.io/4sMD (same video, 23.98 hz, skip 0).
So it means micro judder in X4 box, CE 20 ne.
Unfortunately problem of 23.98 is problem of CE20 ng/ne generally. CE20.1/ng X3 box (X96m+) is doing the same 24 Hz instead od 23.98 
Are you sure that 23.90(as on your picture) is correct value?
It should be 23.98 as minimum or if round up then 24
My LG doesn’t show 23.98 neither on NG nor NE.
GUI of hdmi diagnostics of LG cannot display 23.98 (only 23.90), but there are not skipped frames in Matrix (CE 19.x), in CE 20.x there are, as can you see.
and after push ok on hdmi (right bottom corner)
Try video with 23.976 fps on Matrix and CE20.x, and compare number of skipped frames 0 X many …
I can see micro judder on my 83 Lg oled tv.
I have skip frames only on start while sync correction is going on or if GUI is activated.
And no any microstuttering while watching.
And skip count the same from beginning till the end if video not paused.
X4 Ugoos AM7 box with latest -ne nightly:
In menu from your instruction it’s correct
Try clean install on some other usb/sd and try. May be you have some setting enabled that we don’t see. 
I tried clean install of CE 20/20.1/ne/ng/nightly. Maybe the problem is in used dtb…, in android (Slimbox) its ok, in Matrix its ok.
Its interesting that in revision Plus2 (X96m+, X3) 23.98 hz is ok with CE 20 ng. Problem is with revision T and with Vontar X4.
X96m+ (revision Plus2), CE 20 ng:
Did you make tests with same TV HDMI port?
Yes, Iam testing on 2 tvs, lcd and oled, both the same hdmi. Every box (rev plus2, rev T and Vontar X4) is tested on both tvs. For now X264 is always on 24 hz on X96m+ revision plus2, X265 is 23.98. (CE 20). Its so complicated
A little progress in X3 CE ng 20.1. If I set subtitles to central europe (windows), the refresh rate is by tv detected correctly 23.97 Hz,not 24 Hz. But in X4 CE ne 20.1 is the same 24 Hz. Tomorrow I will be testing on oled tv.
If I set central europe (windows) sub coding on Vontar X4, CE 20.1 ne, Lg oled C2, frame rate of X265 coding is now correct 23.97, X264 still not, still 24.
