That post is completely irrelevant
This one gives the answer:
https://forum.arduino.cc/t/util-delay-h-no-such-file-or-directory/553923
util/delay.h is part of avr-libc, which is a library of code for microcontrollers of the AVR architecture. Any library which uses util/delay.h is only compatible with Arduino boards that use an AVR microcontroller. But you are using the Seeed XIAO, which uses a different microcontroller.
So you won't be able to use this ssd1306xled library. I recommend looking around for other library options. I have seen quite a few libraries for the SSD1306 and I'm certain they offer a wider range of compatibility. You can check the Arduino Library Manager, which can be opened via the IDE's Sketch > Include Library > Manage Libraries... menu.