here below is an attached image from my phone just now. As you can see there is no "jpg" option in this black field at the top of the picture simply buttons for exit, flash and front/rear camera switch.
Here is the screen capture from Huawei P20 PRO (LR Camera pro mode)

Here is the screen capture from Samsung S6 Edge Plus (LR Camera pro mode)

as you can see there is an DNG button switch on Samsung but not on Huawei P20 Pro.
I just spoke with Adobe via chat and they told me that this phone is not on the supported list as pr today and I got not real reason why..
It's very strange that the latest mobile phone with the best camera cannot shoot RAW/DNG within LR while it can shoot RAW/DNG
within its own built in Camera.
When I open the LR and clicks to: () for expanding the menu, than "Device Info & Storage" - "Device Info" - then I see DNG Capture Supported (NO)while it says (YES) on Samsung S6 edge Plus.
So even if P20 Pro is an android phone it does not mean that all features are supported (boring stuff) no phone (as per today) in this world do have a better camera than Huawei P20 Pro so this feature should be supported otherwise there is no point of having pro mode at all.
Clearly Adobe doesn't yet support this phone's raw mode. I would post a request on https://feedback.photoshop.com for support. Adobe might not be aware that their code doesn't for some reason allow raw capture on this phone.