@sven72 The controller can just run on a VM.. Or a docker even - I run mine as a vm on my nas.
You get a better AP, you get a better switch to be honest and more ports. While the UDM and the PRO and what the SE do have market I suppose. They have a new budget one coming out its in EA I think right now that is only 79$ that could be a good seller for them.
I am just really not a fan of all in one boxes.. For big one where that box would go is rarely the correct place for an AP.. 4 ports pretty useless and would need a switch anyway ;)
Once you put all that stuff into one box you limit yourself on features and functions, etc. While you can get a $40 smart switch.. You could also spend way more than that if you want more features at the switch level, etc. AP you can spend way more as well - but the U6 lite is better than the wifi that comes with that udm I do believe.
If you really want to make it work - it can be done, it would end of being a bit of a mess in how has to be configured to be honest.
Just a normal AP or even APs, a switch and your router makes for a clean setup with lots of options for expansion and configuration to really do whatever you would want to do..
There is a market for the UDMs even if your past your return window and want to get your money back. But if you don't want to use it as they intended a all in one box setup, its a pain trying to force it into your network and just use the functions you want.