We reviewed your inquiry and have confirmed that with Intel® NVMe SSDs, the discard option when making your Linux filesystem should be turned off. The default extended option is not to discard blocks at filesystem level, retain this. The discard option is not needed an may actually have a performance impact.
You can find more information about this in the Intel® Linux* NVMe* Driver Reference Guide for Developers.
The best option is to run fstrim, you can actually schedule a cronjob to repeat this process periodically. Here is an external link that provides a good explanation about this:
*NOTE: This link is being offered for your convenience and should not be viewed as an endorsement by Intel of the content, products, or services offered there.
When the TRIM command is executed, it passes the “deleted” file list to the SSD controller. Garbage collection then frees the usable space on the drive.
This process should be quick, especially if little was deleted. This will vary but is normally measured in minutes or less (Approximate time < 1 min on 400GB).