Service Issues: DPF Soot filter full

[SwissXC90]

Oil can only be lost through
1. Leakage out of engine (maybe into coolant)
2. Burning

You can check 1 easily.
NOTE that the engine splash cover contains an absorbent mat that will soak up any leaking oil, so inspect under the engine with no splash cover fitted.
Leave splash cover off and park over a large piece of cardboard, leave overnight and check in the morning. You'll see oil drips on the cardboard easily.

For the 2nd do the following:

Using VIDA do the following:

Check your engine is reaching normal operating temperature of 90°C (+/- 2°). Mine sits happily at 89° C,
Reason: no DPF regens occur until engine is warm; an engine running under normal temperature will never trigger a DPF regen, and the DPF eventually blocks up.

Check your fuel trim on all 5 cylinders. This will show any cylinder with poor compression. Reason: the ECU will compensate for low power on one cylinder by increasing fuel. Good compression on all cylinders with have fuel trim within the specified limits.
NOTE: you don't need a compression testing kit for this - all you need is VIDA software.

Both of the above can be done with VIDA, just by connecting to the car and running the tests.

Especially the fuel trim test is a good indicator of cylinder compression.

If engine temp is normal and fuel trim is normal, then the only place that oil can be lost is through worn turbo oil seals, loosing oil into the inlet or exhaust.

Take of the inlet pipe after the EGR and check for oil
You will have some carbon (soot) but there should be no oil.
Also, check charge air pipe seals under the engine. They may seep a bit of oil.
Disconnect and inspect inside of charge air pipe at the lowest point after the resonator - what does it look like?

I'm picking worn turbo oil seals as likely cause.
Which means removing, inspecting, and likely replacing the turbo.