does OpenWRT support WPA3? Yes, for official release, since 19.07 with wpad-openssl. wpad-wolfssl has been fixed in master/development
does it require special hardware? No AFAIK
any negative issues (like lower performance on older hardware)? In my test case no, the WLAN speed seems to be CPU-bound even without encryption, others with more experience may chime in?
a word about compatibility with other devices (like the mentioned Apple issue) You can go ahead and add later when people report other incompatibilities
is mixed WPA2/WPA3 really more secure than just WPA2? I read that exclusive WPA3 is better, but forgot the details. see reply of huaracheguarache
is WPA/WPA2/WPA3 mixed mode possible? (I see no support for it currently, but what in theory?) no idea, but why would anyone still use WPA?
Fortunately this particular issue with ath9k and draft-n wireless chipsets <= AR9160 will be resolved with mac80211: ath9k: enable MFP capability unconditionally, which I've just successfully tested with on my tl-wr1043nd v1:
Similar efforts have been happening (upstream) for b43 and rt2x00 as well (not yet in OpenWrt); ath5k worked fine with WPA3/ SAE from the beginning. Yes, enabling IEEE 802.11w (which is mandatory for WPA3) on devices that can't do it hardware accelerated does come with a steep performance penalty, but at least it (now-) works - without having to supply module parameters manually.
In theory, perhaps - in practice not at all. Even among the 802.ac chipsets functional 802.11w support is not a given, even less hardware accelerated pmf/ mfp.
Hello, didn't find any info about PC OSes support for this (Windows, OSX, Linux, etc.).
So far I only see it working on Android Q devices (via sharing QR code feature).
Any info about it?
PS: and also I'm interested if Luci interface for that feature exists?