List of Hardware Components is missing oscillator
iCEstick.md's list of Hardware Components is missing the oscillator.
Page 2 of Lattice's document "iCEstick Evaluation Kit User's Guide" mentions:
Discera 12Mhz MEMS oscillator
This shows up as X1 in the schematic in Appendix A. Its output pin 3 is fed to both the FTDI chip's pin 2 as well as the iCE40HX1K-TQ144's pin 21.
Discera looks to now be part of Microchip. No exact part number is given, but it is perhaps one of these:
https://www.digikey.com/short/002nnwhz
Photo of part on iCEstick...
It could well be that they substituted another part without updating the web page, because the marking does not look like any of the ones in the datasheets of Discera (now Microchip).