Ok. I gave up and went for a UBNT US-8-60W together with a UAP-AC-LITE. Not sure if there is any other way to get off-the-shelf a single GUI showing you for all switch/wifi-AP which clients are connected where. I guess if i wanted to go vendor independent, i could have continued to look for switch and AP with SNMP (like the one TP-LINK recommended in this thread) and configured some FOSS SNMP GUI tools, but i think that would have taken me more $$ time than the premium price UBNT takes for its products. And i don't really like to spend time on GUI work.
Besides, i have always had problems on the WiFi side with older gear and various type of APs - routers running OpenWrt, Cisco routers/APs, Netgear, etc. pp. So i figured that going for a big vendor in the higher end residential / small business market would likely give me the best hardened firmware for WiFi when you have a lot of strange wifi gear (disclaimer: Wifi is a mess). And lo and behold, that gear has not had problems since switching to the UBNT AP (knocking on wood).
Next thing is probably to figure out how to install debian on an x86 WAN-edge OpenWrt router so i can put the UBNT controller onto it and have the network infra be independent of any poor linux server PC.
Wish OpenWrt could become more useful for ethernet switches, but i can see how this would be long road ahead and likely too small a market to bother much. And WiFi, my understanding is that there is too much likelyhood for vendor firmware issues for OpenWrt to be of a lot of help ;-(