I have the older version of RuuviTags which does have a bit different ‘carving’ in the PCB, missing few curves.
I can successfully set the bootloader mode and connect with nRF Connect. Uploading the standard firmware package 2.5.9 fails to nRF Connect with error message “Error 6: HW version check failed”
Tried also with the older standard firmware 1.2.12
nRF Connect version is 2.3.2 build 59 on iPhone XS
I have not tried with other phones yet, thus this sounds not being an issue on that end.