OTA file placement

[inigoml]

Hi.
I would like to perform an OTA upgrade. Unfortunately since wifi is disabled (user for AP functionality) I have to use 4G connection in order to upgrade. 2GB take hours or days since my SIM card is for IOT devices and so bandwidth is severely restricted.
How can I perform an OTA manual upgrade from inside Android? I assume that placing img file in a selected location should do the job.
Reformatting SDcard is not a preferred option. There are around 20 partitions and I have to manually delete all of them in order to make Raspberry Pi Imager works again (format does not do the job).
Thanks in advance

[inigoml]

Response to myself:

Just download update, put it in a USB stick, to go Settings -> System -> Updates, press three points upper right, select "Local Update" and choose previously downloaded update. Just that.