Not sure, how active development is right now, but EdgeOS got forked from an open source devian based distro after that went commercial.
But EdgeOS was not the only fork, another one was VyOS (vyos.io). Pretty sure, that EdgeOS has done larger steps forward, especially, since it was bound to the hardware's developer.
The distribution was called Vyatta. VyOS is now very actively used and developed, it's way ahead of EdgeOS since that's been basically dead for years. EdgeOS was basically just a nice web UI over Vyatta but the one key point was that the EdgeRouters had hardware acceleration (Cavium CPU with offload, but Cavium got acquired by Marvell since) and only EdgeOS has the proprietary binary blob and integration that you need to use that on the EdgeRouter hardware.
So even though VyOS exists as the modern day Vyatta fork that is active and fully-featured, you can't really run it on the EdgeRouter hardware and since Ubiquiti stopped development, they're basically e-waste.
I still run one in a network but really shouldn't, since Ubiquiti are very rarely shipping security updates...
Funnily enough, they've just released an update! Yes, I was taken by surprise a bit.
EdgeRouter 3.0.0 [1] adds official wireguard support (I've been using the "wireguard-vyatta-ubnt" package from Github [2]), UI changes and some other improvements/fixes. I haven't tried it yet but will. I have an Edgerouter3-lite and an ER-X.
I'm shocked! Literally two years of basically zero activity since the last hotfix release...
The new GUI looks nice and Wireguard is great! Not all good news sadly though, users in the comments there are pointing out that the kernel has hardly been patched from the versions two years ago... At least some packages like OpenSSH, dnsmasq etc. have had updates.
the one key point was that the EdgeRouters had hardware acceleration
The EdgeRouter Lite used a Cavium SoC, the EdgeRouter X family used a 32-bit MediaTek SoC. Hardware acceleration was buggy on both and is/was known to cause packet corruption.
The main problem with the EdgeRouters was that Ubiquiti was basically just assembling off the shelf stuff. They didn't have the ability to fix SoC issues (or motivate the manufacturers to fix them). For years they didn't have the ability to do much Linux dev work either so the ER families languished on an end-of-lifed'd version of Debian. That experience and realization only motivated me to avoid future Ubiquiti products.
But EdgeOS was not the only fork, another one was VyOS (vyos.io). Pretty sure, that EdgeOS has done larger steps forward, especially, since it was bound to the hardware's developer.