The read & write speed of the boot drive used in the report is way too slow for an SSD which at the very least should be providing closer to 500MB/s transfer speeds even with an older style 2.5" SATA based SSD. Is this external boot drive instead a hard drive? The speeds certainly seem more appropriate for a hard drive especially since the EtreCheck does not mention TRIM at all for this drive, while your Intel external SSD mentions TRIM. If this drive is an SSD, then you have some major issue related to it.
Even if it is a hard drive, the write speed is extremely poor compared to the read speed which is actually quite good for a hard drive. The slow write speed may be due to the use of the APFS file system which tends to perform poorly on a hard drive. Or it may indicate an APFS file system issue. Try running Disk Utility First Aid on the hidden Container on this drive. Within Disk Utility you may need to click "View" and select "Show All Devices" so that the hidden Container appears on the left pane of Disk Utility. Even if First Aid says everything is "Ok" click "Show Details" and scroll back through the report to see if any unfixed errors are listed. If there are any unfixed errors listed, then try running First Aid from Internet Recovery Mode (Command + Option + R), otherwise you will need to erase the whole physical drive and restore from a backup or clone.
Since you have so many other external drives connected, you should disconnect all the other external devices in case one of them is causing a problem. Also connect this drive directly to the laptop and try using another USB-C port especially on the other side of the laptop. You may need to use a different cable and/or adapter.
With so many external USB drives attached, I would suggest using USB3 hubs, adapters, and drives which support UASP which can help with the performance of the drives plus it also helps if you also have older USB1/2 devices connected.
Run DriveDx to attempt to check the health of the drive, but you may need to also install a special USB driver in order to attempt to access the health information from a USB drive. Even with this special USB driver there is no guarantee that the external drive's controller will allow access to the drive's health information. If you can retrieve the drive's health report, then post the complete text report here using the "Additional Text" icon which looks like a piece of paper so I can review it.
