Fedora has a product out there called the ARM imager. It contains built-in support for some common SBC boards, but the Khadas product range isn’t amongst them. I’m not sure they even have any Rockchip SoCs supported at all.
Just getting them to boot will depend on several board-specific tweaks depending on what bootloader they leverage (Petitboot, Uboot etc.) - it’s not like they all have a standardized BIOS/UEFI like a fully-fledged PC does.
Because Fedora is quite militant about their open source policy, any board which requires proprietary closed-source software won’t be directly supported, or only components of the system which do have proper open-source support will work once its installed. A good example is you can image Fedora aarch64 onto an Nvidia Jetson but the GPU component will never work, because it requires a proprietary driver.
Your best bet for support, or at least an intelligent discussion, would likely be Armbian. They are also very much open source purists, do a lot of heavy lifting to get paid peanuts and thus whatever support eventually comes from that project will have parts that work and parts that won’t (IE hardware video acceleration is notoriously hard to achieve)
Please remember the Edge2 is very, very new. The latest news on full Kernel support (AKA, “Mainline Support”) is very thin on the ground. This is recent-ish news on the previous generation Rockchip, the 3568: RK3566 & RK3568 processors to get Linux mainline support soon - CNX Software - so even that isn’t fully working on Mainline as of yet. I have a 3568-based SBC from another manufacturer and whilst is works largely fine on mainline, some common things like hardware mpeg4 decoding won’t work. For that I need a Rockchip-based linux with a proprietary Media Processing Platform (MPP) - I don’t like that, because I don’t know what it does under the hood, and you’ll get a similar answer from most of the rest of the Open Source Community.
These aren’t like PC’s. There’s far less standardization on the hardware side, and in many cases the developers building in support are sitting in front of one of them trying to poke various register addresses directly to get it working. You’ll be deep into the weeds trying to bring one of these boards up and ideally would need to have a background in developing kernel drivers to have a chance.
If I understand correctly, right now all the Khadas builds are probably based off Rockchip’s proprietary linux build which can be cloned from their github repo. To their credit, they’ve done a good job building and packaging it and making it easy for users to install. Rebuilding it all without the proprietary Rockchip stuff is going to be a non-trivial matter.
Last I checked, the status of the Edge2’s SoC the RK3588 - was that it would boot to a console on mainline and that was about it ( Basic RK3588 Support [LWN.net] )