Works better than I expected
The Adafruit LTC4311 I2C Extender works a treat. I need to locate I2C sensors, INA260 and BME280 3m away from the main circuit board. The LTC4311 does the job very well. My research revealed that the LTC4311 worked with Cat5 cable up to 100 feet. I was going to use Cat5 cable, but I had some 4 core flat telephone cable and decided to test using that. Works faultlessly with 5m of telephone cable so I'm happy. Highly recommended.
Edwin Hayward