i got myself an RE450 and im on cable network via RE450. router --> wireless --> RE450 --> cable --> pc i can see WAN Miniport (SSTP) under device manager. what is that?

when sharing data from my phone-data (hotspot) to windows pc, Archer T3U is not finding 5-GHz network. it does find 2.4-GHz network though. can anyone help me? t3u does find another 5-ghz network. how