No worries! It's worth noting that previous generations like ath9k (as you mentioned) and ath10k already support this feature, which is pretty cool.
With any luck, we might eventually see the experts like @Ansuel or @robimarko lend their time to implement this capability for our newer devices too. It would be fantastic to have our current hardware support and benefit from this functionality, bringing it in line with its predecessors. Fingers crossed for future developments!
EDIT: I tested the patch from https://patchwork.kernel.org/project/linux-wireless/patch/1641786090-10232-1-git-send-email-quic_seevalam@quicinc.com/
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Dynalink DL-WRX36 Askey RT5010W IPQ8072A technical discussion - #1762 by Crect
and I'm very happy to report that ath11k + AP/VLAN works well on a custom build based off @arix 's repo!
Added the patch to my copy of @arix's repo here:
https://github.com/gtxaspec/openwrt-mx4300/commit/35c3a6ae76db58c0954e9505c4acd8a4886d18d3 if anyone is interested.