AFAIK, OpenBSD doesn't support .11ac or .11ax at all, with only a very limited number of cards supporting Host AP mode. The only .11n ones I found being athn(4), bwfm(4), and ral(4). The (few) others that support Host AP mode only do so in .11g or .11b. In the future, I would take a look through section 4 of the manual pages, and search the mailing list archives, which could have told you this within a few minutes.
I use (and I believe there are others on here who do as well) an external WAP, that handles only the wireless connections, with DHCP, routing, firewalling, etc., handled by a separate OpenBSD box, the WAP being used only as a bridge. For the OpenBSD hardware portion, you could try https://pcengines.ch APU models, which run from around $130-$180 USD price point, and are well supported by OpenBSD. Unfortunately, they don't have any current stocking information other than "expected ~ 2022."
