To use OpenCV in my Raspberry Pi 3B+ https://pypi.org/project/opencv-contrib-python/
Two materials used in particular: FLIR LEPTON BREAKOUT BOARD V2 and FLIR 2.5 THERMAL IMAGE SENSOR 80HX60V
(J2 Pin) -> (Proper name) -> (RPi connector pin) -> (Cable Color)
P8 -> SCL -> GPIO 3 -> WHITE
P10 -> CS -> GPIO 8 -> PURPLE
P12 -> MISO -> GPIO 9 -> BLUE
P5 -> SDA -> GPIO 2 -> GREEN
P7 -> CLK -> GPIO 11 -> YELLOW
P15 -> VSYNC -> GPIO 17 -> ORANGE
(J3 Pin) -> (Proper name) -> (Cable Color)
P1 -> GROUND (PIN 6) -> BLACK
P2 -> VIN 3.3 (PIN 1) -> RED
Important to increase the SPI buffer size in Raspbian.
SOLUTION:
The problem is in the SPI buffer size. The default value is 4096 but 160x120 images from Lepton3 are bigger.
You need to increase the size of the SPI buffer as explain here
Edit /boot/cmdline.txt and add in the end: spidev.bufsiz= 65535
Then reboot your raspberry and check it worked with: cat /sys/module/spidev/parameters/bufsiz
Hope it works for you also. Maybe this information should be in the README setup tutorial