Once again eBay suggested I buy some DigiSparks. At the price suggested, it was worth a go. They are super for HID keyboard automation. I have needed to reflash the bootloader once or twice.
Note: http://digistump.com is refusing connection.
See this: https://github.com/digistump/DigistumpArduino/issues/167 as http://digistump.com is refusing connection.
Also:- https://forum.arduino.cc/t/digistump-digispark-no-longer-available/1234095
https://raw.githubusercontent.com/digistump/arduino-boards-index/master/package_digistump_index.json
Adding DigiSparks to Arduino IDE.
https://www.instructables.com/Digispark-DIY-The-smallest-USB-Arduino/
This is very helpful: http://digistump.com/wiki/digispark/tutorials/connecting
Drivers and firmware: https://github.com/micronucleus/micronucleus v2.04
https://github.com/digistump/DigistumpArduino - more information
In the box labeled "Additional Boards Manager URLs" enter: http://digistump.com/package_digistump_index.json
I got this when using the board manager and Win10: "CRC error, file corrupted. Try to repeat later"
This helped. https://github.com/arduino/Arduino/issues/9719
I deleted C:\Users\doug\AppData\Local\Arduino15\library_index.json
When I next opened the IDE it seemed to have installed the new boards.
C:\Users\doug\AppData\Local\Arduino15\library_index.json ~/.arduino15/library_index.json
https://github.com/arduino/Arduino/issues/9719 - Win10 reports CRC error
Another may be related problem. The iPhones would not take any updates and failed.
My ISP suggested I upgrade and it seemed to fixed the iPhone update issue.
My old ADSL2 router was replaced by a router that supported FTTC.
I installed DigiSpark into the Arduino IDE over the new router onto a new Windows computer with no issues.