tldr; Turning auto brightness off and setting brightness to the lowest might work.
I have been using the Exynos model for past two years. About a month ago or so the device first exhibited screen flickering issue all of a sudden. Green bars, black screen area, sort of animated and laggy. For the time being, only immediate lock-unlock attempts were causing the screen flickering (meaning, when I unlocked immediately after locking the device, the screen was causing trouble). I left it as it was and just kept avoiding immediate unlocking. Anyhow, after maybe a couple of weeks, out of nowhere the screen appeared to be flickering permanently and the device was rendered totally unusable. I tried doing some troubleshooting, factory reset, odin flash, etc. and none of them worked. Could not visit a service center in this lockdown situation.
Later, I figured that in my case, the screen is working at a very low brightness and partially working at full brightness but not working at all in between. It's just 90% black, 10% green and such. For about a week, I have been using it at a low (i.e. 5% to 10%) brightness. Left the auto brightness, always on display, and screen-on iris recognition settings turned off. I use Bixby or Google Assistant to set the brightness if I can't see the screen. With these setup, it's working for now. As of the software, I am on the latest firmware (May 2020 security patch).
From my observation, the issue had something to do with heating. I am not certain but I feel like the issue occurs more frequently if the device is used for prolonged period and heated up due to gaming or mobile data usage. I would suggest anyone who is stuck during this time before you can repair, should your device work at a low brightness then clean up the phone, get rid of unnecessary apps, games and reduce/avoid long usage that cause heating. Also leave the medium power saving mode on as it limits the CPU usage which supposedly help reducing the heating as well. Do not use night mode, gray wallpapers, etc. Use light or colorful backgrounds, apps, etc.
Thanks. Stay home and safe.
SAME PROBLEM HERE. like... i have to turn off all the high end features. What's the sense of getting a high end phone when you can't use the goddamn high end features? I had to switch to HD Sceeen resolution, i had to adjuat the brightness into 5-10% only, turn ofd Blue Light filter, Scene Mode to BASIC only. Otherwise, the flickering will haunt me again!! I have been using Samsung for like 15yrs now.. most of my phone lasts me 6years and up but this S9 is about 2years only and is exhibiting these errors.. warranty is just for 12mos here in my country. It SUCKS. 😩😩😩
Hurry....Turning auto brightness off and setting brightness to the lowest worked!!!!
Same problem in my S9+ as well for past couple of days. I've the snap dragon version and was using the phone heavily for past couple of week (trust me I was using this strictly for official purpose Teams, Outlook, Powerpoint and very little of prime and other entertainment apps and zero gaming) and it started flickering, green bars, black screen area, animated and laggy, etc,etc. Thanks for your post, after reducing the brightness <10%, its normal now. One more thing I observed is, few apps (youtube, prime, hotstar) were working well even during flickring and green bars etc. Am planning to remove all un wanted apps, but not sure if this problem will pop out again. Lots of questions pops up now, Is there any permanant fix for this, will Samsung provide any solution? Will there be any hardware issue that needs to fixed??
I've been using Samsung phones from S2 till S10 lite for me and my family; didn't except S9+ would create such a issue, this raises trust issue with the brand, hope Samsung will respond...
But you can't enjoy your phone with too low brightness nor too high brightness.. I suggest you also download OLED SAVER in app store while waiting foe Samsung to reply.. it will not fix the actual phone problem but it will stop the flickering and it will save your eyes too much/too low brightness. 😁