The Nano Every is not listed as a supported platform, but since it is similar to the Nano I decided to try it. With a few trivial edits to the code, it does seem to basically work. Starting with the source code in the latest AR488-master.zip make the following changes.
1. In AR488_Config.h uncomment #define AR488_CUSTOM, to choose a custom layout. Since this option does not specify a particular cpu/board type, and does not use interrupts, I hoped that this would avoid most hardware specific code.
2. In AR488_Layouts.h copy the Nano pin definitions to the AR488_CUSTOM section.
3. In AR488_Eeprom.h change EESIZE to 256, since the Nano Every only has 256 bytes of eeprom.
4. In AR488_Eeprom.cpp replace the hard coded constant 512 by EESIZE.
5. The file DEVNULL.h is included in AR488_ComPorts.h, but was not on my Ubuntu system or in the Arduino IDE. Download DEVNULL.h from the web and if necessary, change the include statement to point to the downloaded file.
With these changes, the AR488 project built and could be uploaded to the Nano Every. To test this, I cut an old GPIB cable in half and soldered the Nano Every onto the exposed wires at the end of the cable. This has the advantage that the micro USB port can be brought to the front of the instrument. I'm currently using it to log data from a pair of HP3456a meters, and it seems to be working properly. Obviously, this is not a thorough test, and there might be problems in other applications.
I appreciate the hard work and expertise that went into the AR488 project. Thanks!!