Thank you for the photos, there is nothing wrong with the connections.
That smells indeed like your problem with the R4 all over again: I2C setClock Does not appear to be Standard way to setClock
Can you try the 'I2C_SPEED_FREQ_FAST' as parameter. Can you make an Issue on Github ?
Maybe the BNO086 has troubles with the 400kHz, but it should work with any clock frequency between 100 and 400kHz. I think you don't have to check with other Arduino boards.
A Logic Analyzer can measure the clock and a USB Logic Analyzer can analyze and decode the signals on your computer.
A Raspberry Pi Pico can be turned into a Logic Analyzer, but I have not tried that.
I'm very fond of the LHT00SU1 in combination with sigrok/PulseView. It costs 25 euros. The 5 dollar 24MHz 8 channel Logic Analyzers do work, but the usb connector easily breaks.