Looks like electron 3.x is no longer available for the pi zero.

I had to go back to the old version:

diff --git a/package.json b/package.json
index 14c7874..7a2aff4 100644
--- a/package.json
+++ b/package.json
@@ -58,7 +58,7 @@
     "ajv": "6.5.5",
     "body-parser": "^1.18.2",
     "colors": "^1.1.2",
-    "electron": "^3.0.13",
+    "electron": "^2.0.18",
     "express": "^4.16.2",
     "express-ipfilter": "0.3.1",
     "feedme": "latest",

See also: https://github.com/MichMich/MagicMirror/issues/1500 ; I just undid the change from that patch.

Not sure if that has any other implications, for now this is still installing/building, let’s see if this works.

Max