We are sorry to hear about your experience with the recent updates on your Samsung Galaxy Note 20 Ultra having issues of green and pink line on screen. I feel and understand why you are worried for a device that you've take care so much. If my device is facing similar experience, I will be bothered and disappointed too.
Before you try out the below recommendations as to your solution, be sure to check if your device's software are updated with the latest version. Please check how to update your mobile device's software in the following order.
Step 1. Go to Settings > Software update.
Step 2. Tap on Download and install.
Step 3. Follow the on-screen instructions.
If that doesn't fix the problem, you may submit an error report through the Samsung Members app as follows:
Step 1. Long press Samsung Members icon on Apps screen and tap Error reports.
Step 2. Tap OK on agreement popup to send system log data.
Step 3. Select Symptom category "Display".
Step 4. Describe the problem in details and SEND.
If the issue persists, you may bring your device to the nearest Samsung Authorized Service Center in your area. Rest assured that your device will undergo an assessment to pinpoint the root cause of the issue. Our Samsung engineers and technicians will guide you while offering solutions to restore it.
or book an appointment with the Samsung Members app as follows:
Support > Book an appointment to set one.
Should you need further assistance and guidance, you may contact us via our online Samsung Customer Care support channels below.