@Hank21 

The PC is currently not connected, but it's port had no special setup. As I said before, everything is still pretty much out of the box, except the VLAN 7 for my 5G antenna. DHCP and static ips are handled by my router. I will get glasfiber hopefully later this year and will then switch to OPNsense as my router/firewall, so I didn't want to change setup DHCP, IoT vlans and so on via Omada now, only to change it again a few months later. 

The APs are on Port 5, which has the same settings as Port 4 shown in the screenshot. The three EAP653s are all on Port 5 with a small POE switch in between. 

Testing with my phone worked without problems. I can't provide screenshots now, since I'm not on site (just using the Omada Cloud atm). The IoT devices in question are Shelly Wifi Switches. Those have static ips as well and they provide a webinterface on their ips. I can reach this webinterface and ping them via wifi (no matter if I use a laptop or phone) but I can't access them from a lan connected pc. The cloud connection to the Shelly cloud works without any problems. 

  @Hank21 The Shellys work fine as well, apart from the issue that I can't reach them from a wired pc. Same goes for my phone, I can't ping that from wired lan either. Gateway for all is the router with the dhcp server.

  @Hank21 I can try this next week. However I doubt that it has something to with my router tbh. I already checked the (not very many) options and nothing looks like ACL rules and the router wifi is also deactivated in favour of the EAPs. So from my understanding for the router and therefore the dhcp server every client should be handled the same, right?