How to add a local Electron application to the rootfs of a Yocto build?

Question

Since posting the initial question, I've found a way to get an Electron app onto the rootfs and load it via Systemd, but I still don't know if it's the standard/proper way. I created a deb file of the app via npm, extracted its contents, and copied everything except the Debian package instructions file over to my custom layer's recipe in a compressed tar ball, in a subdirectory named "files". Then, I used the following bb file to install it:

LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

INHIBIT_PACKAGE_DEBUG_SPLIT = "1"
INHIBIT_PACKAGE_STRIP = "1"

INSANE_SKIP:${PN} += "already-stripped"
INSANE_SKIP:${PN} += "arch"
INSANE_SKIP:${PN} += "file-rdeps"

inherit bin_package

SRC_URI += " file://usr.tar.xz;subdir=${BP} "

FILES:${PN} += "/usr/bin/myappname \
                /usr/lib/myappname \
                /usr/share/applications/myappname.desktop \
                /usr/share/doc/myappname \
                /usr/share/lintian/overrides/myappname \
                /usr/share/pixmaps/myappname.png"

Then, to get it to auto-load, I put the following into another recipe for Systemd, with the service file in another subdirectory named "files":

LICENSE = "MIT"
LIC_FILES_CHKSUM = "file://${COMMON_LICENSE_DIR}/MIT;md5=0835ade698e0bcf8506ecda2f7b4f302"

inherit systemd

SYSTEMD_AUTO_ENABLE = "enable"
SYSTEMD_SERVICE:${PN} = "myappname.service"

SRC_URI:append = " file://myappname.service "
FILES:${PN} += "${systemd_unitdir}/system/myappname.service"

do_install:append() {
        install -d ${D}/${systemd_unitdir}/system
        install -m 0644 ${WORKDIR}/myappname.service ${D}/${systemd_unitdir}/system
}

Finally, in the layer's layer.conf file, I added IMAGE_INSTALL += with the recipe names to get the application and Systemd recipes installed.

In my initial attempts, I used Bitbake's devtool, which resulted in a bb file similar to what's shown below, an auto-generated shrinkwrap file, and all the node_modules downloaded in a downloads/npm2 directory at the same level as the build and sources directories.

SUMMARY = ...
LICENSE = ...
LIC_FILES_CHKSUM = "file://node_modules/@octokit/rest/LICENSE;md5=3c37ec01bc4e96607430d51e837a4615 \
                    ..."
SRC_URI = " \
    npmsw://${THISDIR}/${BPN}/npm-shrinkwrap.json \
    "

inherit npm

LICENSE:${PN} = ...

I'm still not sure if devtool would have been proper, and there was a way to use those files, or if there's a reliable way to use the deb file directly (when I tried using that, I ran into errors which led me to the tar ball instead). If my solution is being done in a hacky way and I'm just missing some proven method, I'd love to know.