[Pixel C Android Development] Peregr1ne:
The only parts that to looks potentially suspicious to me is:

knoppix@Microknoppix:~$ sudo fastboot getvar all
(bootloader) version: 0.3
(bootloader) version-bootloader: Google_Smaug.7900.139.0
(bootloader) version-baseband: N/A
(bootloader) product: dragon
[B](bootloader) secure: [COLOR="red"]yes[/COLOR][/B]
...
[B](bootloader) unlocked: [COLOR="Red"]no[/COLOR][/B]
...
all: Done!
finished. total time: 0.281s

Could it be that I missed a step in the unlocking/rooting process?

I'm pretty sure I never ran

fastboot oem unlock

I could try running that but given the other errors (no apparent communication with Pixel when in fastboot) I'm unsure as to how much sense that makes...

For reference the full output included below:

knoppix@Microknoppix:~$ sudo fastboot getvar all
(bootloader) version: 0.3
(bootloader) version-bootloader: Google_Smaug.7900.139.0
(bootloader) version-baseband: N/A
(bootloader) product: dragon
[B](bootloader) secure: [COLOR="red"]yes[/COLOR][/B]
(bootloader) max-download-size: 0x10000000
(bootloader) partition-type:boot: ext4
(bootloader) partition-type:kernel-a: ext4
(bootloader) partition-type:kernel-b: ext4
(bootloader) partition-type:recovery: ext4
(bootloader) partition-type:kernel: ext4
(bootloader) partition-type:system: ext4
(bootloader) partition-type:system-a: ext4
(bootloader) partition-type:vendor: ext4
(bootloader) partition-type:vendor-a: ext4
(bootloader) partition-type:cache: ext4
(bootloader) partition-type:data: ext4
(bootloader) partition-type:userdata: ext4
(bootloader) partition-type:metadata: ext4
(bootloader) partition-type:lnx: ext4
(bootloader) partition-type:misc: ext4
(bootloader) partition-type:persistent: ext4
(bootloader) partition-type:system-b: ext4
(bootloader) partition-type:vendor-b: ext4
(bootloader) partition-size:boot: 0x2000000
(bootloader) partition-size:kernel-a: 0x2000000
(bootloader) partition-size:kernel-b: 0x2000000
(bootloader) partition-size:recovery: 0x2000000
(bootloader) partition-size:kernel: 0x2000000
(bootloader) partition-size:system: 0xe0000000
(bootloader) partition-size:system-a: 0xe0000000
(bootloader) partition-size:vendor: 0x13000000
(bootloader) partition-size:vendor-a: 0x13000000
(bootloader) partition-size:cache: 0x19000000
(bootloader) partition-size:data: 0xd76b00000
(bootloader) partition-size:userdata: 0xd76b00000
(bootloader) partition-size:metadata: 0x4000000
(bootloader) partition-size:lnx: 0x2000000
(bootloader) partition-size:misc: 0x400000
(bootloader) partition-size:persistent: 0x80000
(bootloader) partition-size:chromeos: 0xe8f800000
(bootloader) partition-size:mbr: 0x200
(bootloader) partition-size:gpt: 0x4200
(bootloader) partition-size:RO_SECTION: 0x3f0000
(bootloader) partition-size:RO_VPD: 0x10000
(bootloader) partition-size:RW_SECTION_A: 0x580000
(bootloader) partition-size:RW_SECTION_B: 0x580000
(bootloader) partition-size:bootloader: 0x1000000
[B](bootloader) unlocked: [COLOR="red"]no[/COLOR][/B]
(bootloader) off-mode-charge: 1
(bootloader) battery-voltage: 3835 mV
(bootloader) variant:
(bootloader) battery-soc-ok: yes
(bootloader) Bdev-size:mmc: 62537072640
(bootloader) Bdev-size:flash: 16777216
(bootloader) Gbb-flags: 0x0
(bootloader) Oem-version:RO: Google_Smaug.7132.226.0
(bootloader) Oem-version:RW_A: Google_Smaug.7900.139.0
(bootloader) Oem-version:RW_B: Google_Smaug.7900.139.0
all: Done!
finished. total time: 0.281s