Since this is an unencrypted binary, I'm sure it won't be difficult to reverse engineer. And it will definitely be open source sooner or later. But first, we'll try to convince Rockchip to open source it. Especially since the RK3576 has other proprietary parts, such as OP-TEE and some registers. Also it has a Cortex M0 core, which is also not documented.
Our wifi chipset MT7921AUN has an open driver in the mainline. Of course wifi firmware is binary. But you can use the whole system without a wifi. Main idea is to make the platform open, so you don't need blobs to boot and use the system.
We're currently negotiating with Rockchip and will first try to convince them to open source. This particular binary isn't a problem right now. I'm sure it will be open source sooner or later. All efforts are currently focused on hardware validation, and software is being developed only in areas where hardware verification is required.
[ my public key: https://keybase.io/zhovner; my proof: https://keybase.io/zhovner/sigs/npnGDHrmbrbEr5NAzdgDnicstw0GsYcHBCdTJIbku1U ]