Bought a used P360 tiny for home lab. It came with x16 riser since it used to have a GPU but struck a deal with the seller to keep the GPU(T1000)/RAM(8GB) and storage(512 NVMe) and lower the overall price since I will be replacing those.
I need 10GB networking so I tried a few network cards some with more success than others:
X710-T2L (genuine) - doesn't boot with x16 adapter
X710-DA2 - doesn't boot with x16 adapter
X540-T2 (genuine) - works fine, gets hot
And this brings me to active cooling solution:
Lenovo didn't solder the sysfan connector - had to solder 4 wires from half of a 4pin extension cable (removed WiFi module and antennas to have better access and lower power consumption).

Sysfan is disabled in bios so I had to use 12V w/o PWM

Started looking for a second hand laptop cooler on 12V (most are 5V) that will fit or can be persuaded into fitting inside the case.
Bought the entire cooling solution from an ASUS ROG GL703GM (2 fans with heatsinks and 4 heatpipes) which was hard to repurpose to cool the x540 NIC so ended up with something like this:

Eventually added a shroud to redirect airflow towards heatsink and removed the bracket so the hot air has a way to leave the case with less resistance.
Ordered the x4 riser and MCX311A-XCAT ConnectX-3EN since I wanted SPF+ not RJ45 connector, mostly due to power savings/less heat.

But the tiny included heatsink on MLX runs even hotter (some users reported 89*C) and goes beyond the 55*C working temperature, given enough time in the closed chassis.
Carefully removed a heatpipe from an ASUS ROG GL703GM laptop cooler and some fins from its heatsink and after improvising a mounting solution for long term usage ended up with:

Right now it's idleing in truenas (baremetal) @16.3-16.5W with AMT on and 3m MikroTik DAC.
mget_temp reports 58*C on NIC with normal usage, but it rises fast until the CPU fan speed increases (based on CPU load - will make it ramp up when doing 10G transfers which ends up cooling both CPU and NIC). Haven't seen more than 62*C on NIC but I bet it will go higher.