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Use router APIs on Android 10 devices
Android 10 blocked the retrieval of MAC addresses (among other things) for apps. This is an obvious security feature, and while I disagree with the block (a user request similar to location permissions would be the way to go), there needs to be a workaround.
And the thing is, there is one. Most routers nowadays come with open local APIs to retrieve currently connected devices and some of their metadata (IP and MAC addresses, device name, connection time, just to mention a few). While I understand that this is not a 5 minute feature, adding a few major manufacturers (Asus, Netgear, Xiaomi, D-Link) should be relatively quick, and a great way to replace the native Android API.