If it's not listed as supported, then it isn't supported at all[0], until someone gets it on their desk and tries working on it.
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[0] and there currently isn't a single device with QCN5502 supported by OpenWrt. While it's reasonable to assume that it won't be that much different from its ath79 predecessors, no one knows for sure until someone tries to port it - and it very likely will need some SOC specific changes.