It appears to have changed but I found the original and copied to garagecoder under testing
I copied it here C:\Users\user\AppData\Roaming\garagecoder.gmic and hope you can do something similiar in linux
#********** THRESHOLD ETCH **********
#@gimp Threshold Etch : gcd_etch, gcd_etch(1)
#@gimp : note = note("<i>Replace tones with noise generated lines</i>")
#@gimp : sep = separator()
#@gimp : Threshold Low = int(70,10,255)
#@gimp : Threshold Mid = int(84,10,255)
#@gimp : Threshold High = int(102,10,255)
#@gimp : Threshold Max = int(130,10,255)
#@gimp : Blur Amount = float(0.1,0,2)
#@gimp : Curve Amount = int(1,0,20)
#@gimp : Gamma = float(0.3,0.01,1)
#@gimp : Fast Resize = bool(1)
#@gimp : Color Image = bool(0)
#@gimp : sep = separator(), note = note("<small>Author : <i>Garagecoder</i>. Latest update : <i>2012/03/29</i>.</small>")
gcd_etch : -skip ${1=70},${2=84},${3=102},${4=130},${5=0.1},${6=1},${7=0.3},${8=1},${9=0}
-repeat @# -l[$>]
w={w} h={h} sc=800 ml=4
-if {w>h} nw={min($sc,w)} nh={$nw/w*h} -else nh={min($sc,h)} nw={$nh/h*w} -endif
-to_rgb[0] [0] -if $8 -r[1] $nw,$nh -endif
-b[1] $5% -norm[1] -negative[1] -n[1] 0,255
--c[1] 0,$1 --c[1] $2,128 --c[1] $3,192 --c[1] $4,255 -n[-3--1] 0,255
{w},{h},1,1,0 -noise[-1] 50,2 -deriche[-1] 15,0,x,0
{w},{h},1,1,0 -noise[-1] 80,2 {w},{h},1,3,0 -fc[-1] 0,-20,0 -smooth[-2] [-1],30,30,0 -rm[-1]
{w},{h},1,1,0 -noise[-1] 50,2 -deriche[-1] 12,0,y,0
{w},{h},1,1,0 -noise[-1] 30,2 -deriche[-1] 20,0,y,0
-quantize[-$ml--1] 2,0 -deform[-$ml--1] $6
-repeat $ml -mul[{2+$>},-1] -done
-add[-$ml--1] -n[-1] 0,255 -rm[1]
-negative[-1] -apply_gamma[-1] $7
-if $8 -r[-1] $w,$h,1,3,5 -c[-1] 0,255 -endif
-if $9 -compose_shapeaverage[0,1] -else -keep[-1] -endif
-endl -done