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Power may be the issue as the AMPS on the Retina is rated to 4.3 and the WD15 is rated 6.7A/9.23A
 
I just picked up a 12" M5 2016 Macbook during the last BF. I also have the WD15 that I am using with my Dell XPS 15 9550.
With fully up-to-date firmware, the dock works very well for my setup.
Connected to the WD15 dock are
- One Dell U2412M (1920x1200) through Display Port
- Logitech unifying receiver for keyboard and mouse
- Gigabit Ethernet Cable
- External USB drive (WD Passport 3TB)
- Headphone
As far as I know, everything works, the dock charges the Macbook (Approx 20W).
It also works in a clamshell mode.
Seems to be an ideal docking solution.

-- Update --
Dual monitor sort of working. The two display can only mirror each other. It does extend from the Macbook built-in LCD but the two external monitors can only display the same thing.
Did you ever fix the dual monitors mirroring each other. Did you ever get them to extend?
 
Did you ever fix the dual monitors mirroring each other. Did you ever get them to extend?

No, I have learned that this is a limitation of all Macbook Retina. Apple disabled the MST over the USB-C so it's impossible to get dual monitor output from a single connector.

One way to work around it is to buy a USB display link adapter like this one (I haven't personally tried this, but I heard it works)
Hook up the display link adapter to the USB-A port in the WD15. That way you'll get 2 HDMI port that can be extended. (or use the Apple USB-C to HDMI multi port adapter for a cleaner setup)
Good luck
 
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For me the TB15 is working mostly fine.
LAN, most USB Slots, HDMI (1080p) and Audio works pretty good.
BUT.. I can't get the USB C Port working. It works on my MacBook Pro 2016 Touch Bar running the Windows on Bootcamp but not on OSX.. Anyone having any experience with that?
 
SOLUTION:
I now found a solution! Reboot the Mac in safe mode (Reboot and hold down SHIFT). Reboot again to normal mode and the WD15 works!
Amazingly, that's fixed the problem of my Mac not charging with this dock (Dell WD15). I don't know how long it will last, but so far, so good.
 
I have a Dell WD15 and a 2020 macbook air (intel, thunderbolt 3). It worked up until a month ago when an update broke it and now everything works except video (macbook resolution even changes and recognizes the display like before). Rebooting in safe mode then back didn't work for me. I haven't tried the TB3unlocker since I don't really know what I'm doing.
 
DELL WD15+ Macbook Air M1 / iiyama XUB2792QSU /ethernet /usb (mice keyb) all works... but sometimes not.
I also use the same config with a Dell laptop from my work ,and when i swap computers , the mac doesnot display on the monitor.
I dicovered that when i sort of reset the dock by unpowering the dock , repowering and then plug in the USB-c of the mac i'll get all functions.if not-> no display ,but ethernet and USB always works.
works on HDMI and Displayport with 2560x1440 on 60 and 70Hz.
Once in "mac mode" i can unplug the mac and plug it back in -> it works
Connecting the Dell back will always work. but it somehow gets in "dell mode"
Checked today and WD15 has the latest firmware. MBA runs 11.6.2
 
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