Same issue like a lot of other people has reported. My new disk is performing absolutely terrible. Seems to be fixed with firmware 3B2QGXA7.
How can a Linux user get the new firmware? It is not listed on https://www.samsung.com/semiconductor/minisite/ssd/download/tools/
In the firmware listing on that site is an NVME installation guide explaining how to create a booting Linux USB drive for the firmware update once 3B2QGXA7 is released into the wild.
Do you have a friend with a spare Windows NVME slot?
Reading stuff is fun!
Dear Linux users that might find this post.
Initially the new firmware did not fix the issue for me. After a few days of rage I can conclude that Linux users should NOT use TRIM on the device. After I disabled fstrim service and did a reset of disk with samsung ssd dc toolkit it now performs almost as advertised.
Now lets see what happens when the disk starts filling up..