I finally found the solution! The lack in the file above was for libudev!
First of all, I was able to find this solution by pulling both the electron zip file and the debug file from Release electron v9.0.2 · electron/electron · GitHub. It was important for me, after unzipping both, to move the .debug files into the same directory as my electron executable. I was then able to run electron, then apply gdb to the core dump.
ls -1
-rw-r--r-- 1 savanni users 179981 Jan 1 1980 chrome_100_percent.pak
-rw-r--r-- 1 savanni users 321151 Jan 1 1980 chrome_200_percent.pak
-rwxr-xr-x 1 savanni users 6322128 Jan 1 1980 chrome-sandbox
-rw------- 1 savanni users 213487616 Jun 26 21:40 core.11309
-rw------- 1 savanni users 203784192 Jun 26 21:45 core.12031
drwxr-xr-x 2 savanni users 4096 Jun 26 21:45 debug
-rwxr-xr-x 1 savanni users 129796744 Jan 1 1980 electron
-rwxr-xr-x 1 savanni users 1500482568 Jan 1 1980 electron.debug
-rw-r--r-- 1 savanni users 1067459225 Jun 26 21:41 electron-v9.0.2-linux-x64-debug.zip
-rw-r--r-- 1 savanni users 73660512 Jun 26 21:44 electron-v9.0.2-linux-x64.zip
-rw-r--r-- 1 savanni users 10505952 Jan 1 1980 icudtl.dat
-rwxr-xr-x 1 savanni users 243992 Jan 1 1980 libEGL.so
-rwxr-xr-x 1 savanni users 1980936 Jan 1 1980 libEGL.so.debug
-rwxr-xr-x 1 savanni users 3103488 Jan 1 1980 libffmpeg.so
-rwxr-xr-x 1 savanni users 6316832 Jan 1 1980 libffmpeg.so.debug
-rwxr-xr-x 1 savanni users 8948960 Jan 1 1980 libGLESv2.so
-rwxr-xr-x 1 savanni users 16141232 Jan 1 1980 libGLESv2.so.debug
-rwxr-xr-x 1 savanni users 4488304 Jan 1 1980 libvk_swiftshader.so
-rwxr-xr-x 1 savanni users 43791632 Jan 1 1980 libvk_swiftshader.so.debug
-rwxr-xr-x 1 savanni users 8483376 Jan 1 1980 libvulkan.so
-rw-r--r-- 1 savanni users 1060 Jan 1 1980 LICENSE
-rw-r--r-- 1 savanni users 4710103 Jan 1 1980 LICENSES.chromium.html
drwxr-xr-x 2 savanni users 4096 Jun 26 21:45 locales
drwxr-xr-x 87 savanni users 4096 Jun 26 21:19 node_modules
-rw-r--r-- 1 savanni users 299 Jun 26 21:19 package.json
-rw-r--r-- 1 savanni users 27518 Jun 26 21:19 package-lock.json
drwxr-xr-x 2 savanni users 4096 Jun 26 21:45 resources
-rw-r--r-- 1 savanni users 4791423 Jan 1 1980 resources.pak
-rw-r--r-- 1 savanni users 1399 Jun 26 21:48 shell.nix
-rw-r--r-- 1 savanni users 50592 Jan 1 1980 snapshot_blob.bin
drwxr-xr-x 2 savanni users 4096 Jun 26 21:45 swiftshader
-rw-r--r-- 1 savanni users 170903 Jan 1 1980 v8_context_snapshot.bin
-rw-r--r-- 1 savanni users 5 Jan 1 1980 version
-rw-r--r-- 1 savanni users 107 Jan 1 1980 vk_swiftshader_icd.json
[fhs-shell-env] savanni@garnet:~/s/electron-env $ gdb electron core.14496
GNU gdb (GDB) 8.3.1
...
Reading symbols from electron...
Reading symbols from /home/savanni/src/electron-env/electron.debug...
...
warning: Unexpected size of section `.reg-xstate/14520' in core file.
#0 0x0000562334b7f493 in device::UdevLoader::Get()::$_0::operator()() const (this=<optimized out>)
at ../../device/udev_linux/udev_loader.cc:38
38 ../../device/udev_linux/udev_loader.cc: No such file or directory.
[Current thread is 1 (Thread 0x7fcf4e9bd700 (LWP 14520))]
So, as soon as I add libudev to the shell description above, I have everything I need to launch an electron app!