Secure boot disables trim on external drives

I have a Promise Pegasus2 R6 configured as a RAID 5 and an OWC Thunderbolt 4. Both are Thunderbolt 2 devices, so I use Apple’s Thunderbolt 3 to Thunderbolt adapter to connect the enclosures to the iMac Pro. The computer starts up fine from the OWC enclosure; the Pegasus2 does not have a system installed on it. Note that the iMac Pro’s default setting for Startup Security is to not allow booting from external drives, so you’ll need to change that in the Startup Security Utility.

I have a workaround for the issue of Secure Boot disabling Trim on external drives. I'm posting it in case it helps someone else. In order to have Trim enabled on external SSD's when running with Secure Boot enabled, the SSD's need to be unmounted when starting up the computer. When the SSD's are subsequently mounted, Trim will be enabled.

I discovered this after reading about a similar issue with Secure Boot and SoftRAID drivers (which, for clarity, I do not have installed.) In that case, SoftRAID volumes need to be mounted after booting up (when Secure Boot is enabled), in order for the latest drivers to be used. SoftRAID explained that if macOS detects SoftRAID volumes at boot time, it will load the default SoftRAID drivers included with macOS, i.e. those "approved" by Secure Boot, which are not the most current drivers. By mounting SoftRAID volumes after booting up, macOS loads drivers at that time, using the most current versions installed on the computer.

I thought a similar approach might be used for Trim. It seems likely that whatever Trim-related ktext is loaded at Secure Boot is not the one effected by the Trimforce command, but that by having no SSD's mounted at boot time, the needed ktext is not loaded until the SSD mounts after boot and, in that case, macOS loads the one effected by Trimforce.

While I only understand your response in a vague way (not being familiar with the details), it might explain why Cindori's Trim Enabler also failed to work with Secure Boot. Thanks for responding.