Gimhook creator here. Do you have crostini (The crosvm-based linux environment inside of ChromeOS) enabled?
If you care about speed (on lower-end chromebooks crostini can be very slow if you’re not careful), the RW_LEGACY trick works really well. And as the above screenshot (which is real, by the way) states too, I personally do that trick. However, you’ll need a flash drive with a linux image on it (I use Debian and occasionally postmarketOS in my case) and some knowledge of GNU/Linux things. Gimhook 0.1.0-rc3 was actually built and published from a Chromebook in RW_LEGACY mode, no joke
However, crostini is by far the easiest way to do it, and works seamlessly with other ChromeOS apps. Admittedly I haven’t tested Gimhook on it, but the only issue I know of would be performance, and that depends on the chromebook and ChromeOS version.
There is no one source for mods… at least not yet… There was an attempt to make a mod database at Enhanced Movement | Gimhook Wiki, but it was unofficial (I didn’t make it) and completely dead nowadays.