How long have you had the router and how long have you had this ISP radio service?
The ISP being on 2.Ghz even though the router has 2.4Ghz, I wonder if there could be any interferences. Frequency is kind close. Something to look at.
Out of these devices you have, what devices support 5Ghz if any?
Camera System
Nest thermostats
IP Cameras
2 Printers
3 Laptops
2 Workstations
2 Tablets
1 Solar Array Grid
3 Smart TVs
5 Smart Blue Ray players
2 Amazon fire sticks
You have quite a few wireless devices. Are they all connecting to the 2.4Ghz radio or any of them connecting to the 5Ghz radio...
You might do the following, Turn off as many wireless devices as you can and start testing with a couple or just high priority or devices that need access and see how the router operates. After a while, start adding one device at a time to see if the problem appears...
Also set IPv6 to Local Connection only...