Thank you Nicola,
The i-tec uses the same principle, and you can see the same
4Kp30 limitation on the HDMI output.
For the Dell D3100, you are correct. This is a DisplayLink only solution. It has a dual-chip design of our previous generation chip. It can do 1x 4Kp30 + 2x 1080p.
The displays are driven directly from the dock output.
The dock isn't a GPU so the computation is still done on the laptop GPU.
Unlike Alt-Mode which doesn't go through standard USB hubs, you can daisy-chain DisplayLink technology. Therefore, you could wish to keep the future-proof aspect of the Dell D6000, and add a single head USB -> HDMI adapter. That adapter could also be useful when travelling or in meeting rooms as well: conference room system input, projector, TV...
Your next machine would have USB-C Power Delivery for charging, and this isn't possible over USB-A.
Kind regards,
Alban