Update device (smartplug) firmware with Conbee II on HA OS

I am trying to update a device (a TS011F TZ3000_typdpbpg or similar Tuya smart plug) firmware. I run Home Assistant OS (9.3), latest HA version (2022.11.5) and use a ConBee II USB stick plugged into a Raspberry Pi 4. The interfaces to the Conbee device are through the deCONZ add-on in Home Assistant, and I can connect (through this add-on) via the Phoscon Web App or the deCONZ application (via some HA builit-in VNC server).

I can see the device I want to update in the “OTA Update” tap in the deCONZ application. It has vendor ID 0x1141, image 0xd3a3. I found what I believe is the latest firmware on https://images.tuyaeu.com/smart/firmware/upgrade/20220907/1662545193-oem_zg_tl8258_plug_OTA_3.0.0.bin.
The screen in the OTA Update tab shows a OTAU File select button, and what I think I need to do is select this firmware file and update the device.

There are plenty of manuals online describing device firmware update, but all skip over some steps, how to get the file on the file system of the ConBee, so I can select it?

I suppose there are many combinations of deConz hardware, domotics platforms, OS, installation options like docker containers, etc. None seems to apply to mine, of which I thought it was pretty standard.

Who can help me out? I try to understand what is happening ‘under water’. But what I see in the deConz application, is that something running on the OS of the ConBee stick, or on my raspberry pi running HA, in some virtual environment? The file system shown in the deCons app, it seems not to be the on on my Raspberry Pi. Or is it a private folder structure in some container? Or is this an OS on the deConz stick? I can open a terminal to my HA installation (HA plugin), but that shows a different file structure. The VNC connection to the deConz app doesn’t show an IP address or port I could connect to with another VNC client from a windows laptop for example. So how do I get there? Or can I open a terminal on deConz (how?) and wget the firmware file directly to it? I have no clue.

Please guide me, preferably with a manual that applies to the same combination of elements as I stated above.