Not sure which country are you from.
I am from Malaysia and faced the same issue, was playing game one evening, and suddenly green line appeared, and over the time each day appear 1 extra line. Sadly the warranty period has lapsed.
Went to a nearby service centre, was informed that the cost of it minimum MYR1000 (~USD233), whereby the cost of the phone was MYR4000 (~USD932). When questioned what was the issue, the service person just mentioned that either i have dropped my phone and damaged the hardware or i have been putting tremendous amount of pressure on the screen. I do admit that i drop my phone, low height or often landing on soft surfaces, but the line did not occur once i drop the phone.
When i reached out to their customer service- not helpful at all, i then reached out to UK's CEO office via a form on UK's Samsung contact us page, finally someone gave me a call and offered me discount on my next phone purchase, but due to warranty expired, they will not be able to cover the fees or waive partially for the fix. Claiming that the article i read was due to a software issue. Of course he did not "accuse me" of anything since the call is recorded, but one can tell they are indirectly saying its my fault, whereby i admit, but not fully my fault.
I have been doing my research reading enough forums and tech news portal - the information provided back then (i think dated around Sept-Nov 2021) the issue can be resolved by updating the software or factory reset, but still some people didnt know their rights and paid for the repair whereby it is a known issue for S20+ to have this green line issue (S20 Ultra to have the whole white or green tint).
Currently i am collecting data and reading up enough forums and tech news portal to file a complaint to consumer tribunal (some countries have Ombudsman to do so).
After the call, literally went to an Apple shop and got myself an iPhone. I've totally lost trust on Samsung and their after sales service. Not trying to flex, but just show how frustrated i am and so done with their **bleep**.
If anyone else has any way of helping, please do drop me a message.
P/S im not some one that is so tech savvy or knows the technicality, hence all i can rely on are forums and news portal.
Good luck with your issue.
