27" iMac Kernel Panic

iMac Model: iMac17,1

3.3 GHz Quad-Core Intel Core i5 (i5-6600) CPU: 4-core

16 GB RAM - Upgradeable

BANK 0/DIMM0 - 8 GB DDR3 1867 👈🏻

BANK 0/DIMM1 - Empty

BANK 1/DIMM0 - 8 GB DDR3 1867  👈🏻

BANK 1/DIMM1 - Empty

Are the two 8GB RAM modules the ones that shipped with the computer, or has the computer been upgraded with aftermarket RAM? I ask because many kernel panics are related to RAM, either poorly-seated, low-quality, or incompatibility. Removing and reseating the RAM modules is a good diagnostic step and quite easy with a 27-inch iMac.

If upgraded with Crucial or OWC modules, RAM is unlikely the cause of the KPs. Others can be suspect.

Your SSD speeds are currently running on the nominals for that drive configuration, but may not stay there without TRIM. Engaging TRIM on your internal SATA SSD is important because, without it, the Write speed will eventually start to decay and slow overall operation. Been there, done that. My Writes fell from 500MB/sec to under 60MB/sec before another contributor here clued me in on the need for TRIM.

Instructions for enabling TRIM on that drive are here. What is not mentioned in that article is to do a Safe Mode boot when done. Let the computer "soak" in Safe Mode for 30-60 minutes before doing a regular restart. That allows Safe Mode time to do its housekeeping. As you have a lot of free space, yours may to take that long.

As an aside: The article I linked was published by OWC who, in the text, say TRIM is not required for their drives. My drive that slowed without TRIM is an OWC model. Engaging TRIM restored it original speed and it is still fast today.

There is no evidence that this computer is backed up, this means there is almost a 100% guarantee you will lose your data. If for some reason you are not aware of Time Machine (Apple's backup app), please refer to Back up your Mac with Time Machine and backup ASAP before you do ANYTHING else.

Also, the SSD that was installed does not have TRIM enabled. I would recommend that you use DriveDX and run a report on all of the drives (internal and external) connected to this machine. If ANY errors appear that indicates the drive is failing and must be replaced. However, on an obsolete and Vintage machine (what a 2015 iMac is classed as) I would strongly recommend considering replacing the computer rather than putting $1 into it.

KPs can be caused by either hardware or software. Common hardware issues are failing drives (either internal or external drives attached to the computer), RAM (incorrect, failed or unseated RAM), failing internal components such as a GPU, cables, etc.

Software issues can be caused by an extremely wide variety of issues however none are obvious from your EtreCheck report, try running Malwarebytes to see if you installed any malware.

Otherwise as with other DIY projects you are pretty much on your own. This is why when doing hardware upgrades such as SSDs they should be done by an Apple Authorized Service Provider so when it goes south, you have someone to go to.

Best of luck.