How do I move apps to Micro SD card in Nokia 6.1 (Android One) device?
The Nokia 6.1 has a reported issue with using SD card as internal storage,
detailed on the XDA Forum.

To summarise: 
The ability to use an sdcard as internal storage is avaiable with build 00WW_3_206_SP01 
However, users have found files put on to the sdcard get corrupted at random 4096-byte boundaries.

In terms of options open to you, Google Play does have the instant app, which allows the user to use apps without installing them on the device. This might help in a small way.