I have a Bluetooth Low Energy Android app project here which works fine so far for most of my android smartphones. I use my BLE weather thermometer in my app anywhere within my room, it works.
Except for a Huawei P30 Lite deivce: With my Huawei I can not get a connection, except I place the BLE Thermometer on my right upper corner on my Huawei smartphone. I assume the Bluetooth antenna is located there in my smartphone?
Under linux I can configure my wifi transmission power like:
sudo iwconfig wlan0 txpower 30mW
Is there such a possibility to configure my Bluetooth Low Energy Android library?
It is not obvious from your question where the problem is. Typically in Bluetooth you have control of the power the peripheral advertises at, so that would be the BLE weather themometer in your case.
I would suggest looking at the HCI logs on the phones to see if they give more insight as to what the issue is.