I don't know this. I have a nano pi k2 board. Is there any way to make an openwrt firmware? thank you very much
There are no concerted plans to support any device, device support is contributed by users owning the device and wanting to run OpenWrt on it (e.g. by you). If there are no interested users investing time and money (to buy their device and the equipment necessary for development, e.g. soldering stuff, serial console, flash writer etc.), the device might never be supported.
In general, the better SOC- and driver support for a given device in the mainline kernel, the easier it typically is to add support. If at least SOC support already exists in OpenWrt (for similar devices), one can often piggy-back on these efforts and add support reasonably easy - adding a new target requires more efforts. At least the experienced users obviously check the chances of adding support before buying a device, meaning a device without existing SOC support would have to be very attractive for anyone to feel confident enough to spend the efforts of adding a new target from the ground up.
Mainline SOC support for amlogic is somewhere between non-existent and bad, OpenWrt doesn't have prior support for these targets either, so expect a steep battle to get it working.