Hi David,
When you reflash the SD card using the Brennan 'B2BNov2019.zip' file, and plug the microSD card back into the B2, the software version will first show as 'B2B Nov 6 2019'.
Then you run 'Web Upgrade' one time and you will find that the software version will show as 'B2B June 2 2020'.
The later model B2s do require the case to be opened, but that is a relatively straight forward task. The website instructions are very good. Just be gentle while opening the case, and only pull the back out by 3 cms and you will be fine!
Regards,
Peter.