Macbook Pro 16 Thunderbolt ports dead/damaged twice after used with Samsung CJ89 43" monitor with USB-C
I know you’re frustration and you’re hoping against hope that it’s something simple, but the evidence is pointing to a defective monitor. Apple may decline warranty service for this second repair if plugging into the same monitor causes the same issue.
I answered a very related question regarding monitors and warranties.
Is it safe to connect external screen to MacBook via USB-C from the warranty perspective
In short, you should feel confident that plugging in your monitor, especially a known brand like Samsung is a safe procedure. However, if it’s found that the monitor is what is the cause, they may direct you to Samsung to cover the repair costs - and would legally be within their rights to do so. Samsung isn’t perfect, nor is Apple and it’s not unreasonable that Apple decline something that‘s not their fault.
I’m not a lawyer and this should not be construed as legal advice, just my opinion based on many years of this type of experience.
Bottom line is you may get it repaired or you may not.  But, if you do, before plugging it in for a 3rd time, it would be in your best interest to not plug you Mac into that monitor until you get it checked out.
In fact, as a DYI test, you can try a USB-C meter inline with another device (like a sacrificial Android tablet) and see what your power is being sent by the monitor. Anything cheap and you don’t mind losing. Anything but your Mac. If you see  more than 20V @ 5A and/or you fry the test device means  you’ve definitely got a problem with your monitor.
It’s highly unlikely Apple will fix this a third time