For Ubuntu:
Open the Software & Updates program and select Community-maintained free and open-source software (universe)
In a terminal, run: sudo apt update && sudo apt install make gcc gcc-avr avrdude avr-libc build-essential
To get patch files from GitHub, click on the commit and in the URL, append .patch and then save that as a .patch file.  pandrew's work to create 0.9.2 firmware can be found here:  https://github.com/purdeaandrei/ibm_capsense_usb_mods/commits/master
Move the patch files into the src directory
In the terminal cd into the src directory
To change the files based on a patch file, run patch < filename.patch
Run patch files in order from oldest to newest (start with debounce patch, then patch 1, then patch 2, then patch 3 (the latter three patches from pandrew).
Run make and copy the ibm_capsense_usb.hex file that was created
The default debounce is 11. To create the debounce 6 version, edit the scan.h file and change the line with #define SCAN_DB_THRESH_TOP 11 - change to a 6 (I use the debounce 6 version when sending out the Brand New Model F keyboards)
Run make and copy the ibm_capsense_usb.hex file that was created
