Flatpak manifest for Scratch Desktop 3.0

edu.mit.scratch.ScratchDesktop.json

{
    "app-id": "edu.mit.scratch.ScratchDesktop",
    "runtime": "org.freedesktop.Platform",
    "runtime-version": "18.08",
    "base": "org.electronjs.Electron2.BaseApp",
    "base-version": "18.08",
    "sdk": "org.freedesktop.Sdk",
    "command": "scratch-desktop",
    "separate-locales": false,
    "finish-args": [
        "--share=network",
        "--share=ipc",
        "--socket=x11",
        "--socket=pulseaudio",
        "--device=dri",
        "--filesystem=home",
        "--talk-name=org.freedesktop.Notifications"
    ],
    "modules":[
        {
            "name": "electron-x86_64",
            "only-arches": [ "x86_64" ],
            "buildsystem": "simple",
            "build-commands": [
                "mkdir -p /app/bin/resources",
                "cp *.so  /app/bin",
                "cp *.bin /app/bin",
                "cp *.dat /app/bin",
                "cp *.pak /app/bin",
                "cp electron /app/bin/",
                "cp -r resources/ /app/bin/"
            ],
            "sources": [
                {
                    "type": "archive",
                    "url": "https://github.com/electron/electron/releases/download/v3.0.4/electron-v3.0.4-linux-x64.zip",
                    "sha512": "9e0febf884f652bc0b33088c87de4eba197e92283526e31ec3c51d649cf029da1b32d6fe5588acaa4420b8f74ea4f7e68ddf125f2c3b457eabbf766119212e76",
                    "strip-components": 0
                }
            ]
        },
        {
            "name": "electron-i386",
            "only-arches": [ "i386" ],
            "buildsystem": "simple",
            "build-commands": [
                "mkdir -p /app/bin/resources",
                "cp *.so  /app/bin",
                "cp *.bin /app/bin",
                "cp *.dat /app/bin",
                "cp *.pak /app/bin",
                "cp electron /app/bin/",
                "cp -r resources/ /app/bin/"
            ],
            "sources": [
                {
                    "type": "archive",
                    "url": "https://github.com/electron/electron/releases/download/v3.0.4/electron-v3.0.4-linux-ia32.zip",
                    "sha512": "0b9d297718c45215ddf5ec26e174435c90537e10fd84356f1e0c398b2d3acbc0aca003322d6748111f1b45923f9ebecd02e58843eca9ec1a3268ecd7702792e9",
                    "strip-components": 0
                }
            ]
        },
        {
            "name": "electron-arm",
            "only-arches": [ "arm" ],
            "buildsystem": "simple",
            "build-commands": [
                "mkdir -p ${FLATPAK_DEST}/bin/resources",
                "cp *.so  ${FLATPAK_DEST}/bin",
                "cp *.bin ${FLATPAK_DEST}/bin",
                "cp *.dat ${FLATPAK_DEST}/bin",
                "cp *.pak ${FLATPAK_DEST}/bin",
                "cp electron ${FLATPAK_DEST}/bin/",
                "cp -r resources/ ${FLATPAK_DEST}/bin/"
            ],
            "sources": [
                {
                    "type": "archive",
                    "url": "https://github.com/electron/electron/releases/download/v3.0.4/electron-v3.0.4-linux-armv7l.zip",
                    "sha512": "44843381e650c77a49da4262e5f274cd6db91deb669c5d2038e5c635d1842fa9abf766169eb732e14716cc48a227154588ce52ecb86d5502fbf29d35429a990f",
                    "strip-components": 0
                }
            ]
        },
        {
            "name": "electron-arm64",
            "only-arches": [ "aarch64" ],
            "buildsystem": "simple",
            "build-commands": [
                "mkdir -p ${FLATPAK_DEST}/bin/resources",
                "cp *.so  ${FLATPAK_DEST}/bin",
                "cp *.bin ${FLATPAK_DEST}/bin",
                "cp *.dat ${FLATPAK_DEST}/bin",
                "cp *.pak ${FLATPAK_DEST}/bin",
                "cp electron ${FLATPAK_DEST}/bin/",
                "cp -r resources/ ${FLATPAK_DEST}/bin/"
            ],
            "sources": [
                {
                    "type": "archive",
                    "url": "https://github.com/electron/electron/releases/download/v3.0.4/electron-v3.0.4-linux-arm64.zip",
                    "sha512": "7e0bde12d3b2e1ea8ee7545239092d786cf84b9e411a047c19e0188bc0a500eb6574ef9c60a4f26e2abce7fb3d823baa5947c09c4df6b052c153a07c7da7dcc2",
                    "strip-components": 0
                }
            ]
        },
        {
            "name": "p7zip",
            "buildsystem": "simple",
            "build-commands": [
                "cp makefile.linux_any_cpu makefile.machine",
                "make 7zr",
                "install bin/7zr /app/bin"
            ],
            "cleanup": [
                "*"
            ],
            "sources": [
                {
                    "type": "archive",
                    "url": "https://vorboss.dl.sourceforge.net/project/p7zip/p7zip/16.02/p7zip_16.02_src_all.tar.bz2",
                    "sha512": "d2c4d53817f96bb4c7683f42045198d4cd509cfc9c3e2cb85c8d9dc4ab6dfa7496449edeac4e300ecf986a9cbbc90bd8f8feef8156895d94617c04e507add55f"
                }
            ]
        },
        {
            "name": "scratch-desktop",
            "buildsystem": "simple",
            "build-commands": [
                "7zr x scratch-desktop.exe",
                "cp resources/app.asar /app/bin/resources",
                "cp -r resources/static /app/bin/resources",
                "ln -s /app/bin/electron /app/bin/scratch-desktop"
            ],
            "sources": [
                {
                    "type": "file",
                    "url": "https://downloads.scratch.mit.edu/desktop/Scratch%20Desktop%20Setup%201.2.1.exe",
                    "sha512": "35aebf51772bd1d23076c192925630ad4ac02ff6a10ef2b9cf7cc5163d7410c153b834832dec7d466ee7f5e613251d0830338bb72cedf434510eb14cab6fd92f",
                    "dest-filename": "scratch-desktop.exe"
                }
            ]
        }
    ]
}

With this file saved as edu.mit.scratch.ScratchDesktop.json you can build and install a Flatpak like this:
flatpak-builder --user --install-deps-from=flathub --force-clean --ccache --repo=repo --install build edu.mit.scratch.ScratchDesktop.json

Then run with:
flatpak run edu.mit.scratch.ScratchDesktop

It doesn't have any desktop file / icon / metadata but that's not too hard to add. If I can figure out the license (ie, is the app.asar redistributable) we could submit to https://flathub.org.

Thanks to https://gist.github.com/lyshie/0c49393076b8b375ca1bd98c28f95fb0 for the pointer. :)