I'm not actually an expert on these devices, but I'm afraid that I'm pretty sure that's a clone. A web search on the baseband version indicates that that baseband corresponds to firmware for a MediaTek MT6589 SoC, not the Kirin 970 that the P20 Pro should have. These clone devices are usually programmed to lie about their identity, android version, etc, but the basband firmware is usually reported correctly which is why that's the first thing I check.
That explains why HiSuite won't work with it, because it isn't a Huawei device. I hope you got it for a good price, because the MT6589 is an older much less powerful SoC than the Kirin 970, and probably other components are similarly cheaper and lower-end than they should be. The whole business model of clone manufacturers is to produce the cheapest possible device they can pass off as something newer: in the best case they sell to someone who wants people to think they have a fancy new phone and know they are buying a fake, worst case they try to con people by selling it as the real thing.
What's worse is that it's probably actually running Android 5. Note that it says "Android 8.1 / Lollipop MR1": Lollipop is Android 5 (many clone manufacturers do a better job of hiding it than this). Also the MT6589 is a 2013 processor, and I doubt that MediaTek ever produced drivers for it for anything later than Android 5 (most 6589 devices run 4.4, and at that time MTK-based devices were infamous for never getting software updates). As I say I'm not an expert on these devices, so you might get lucky, but I really don't think you've any chance of actually running Android 8 on this phone.
Unfortunately I have no good news on firmware. It won't be easy to identify what device it really is, and if you don't know that you've no chance. Even if you can identify it it's likely that there is no newer firmware. Sometimes these clones are based on the same platform, and sometimes you can find firmware for that platform, but I'd want to be very, very sure that it's exactly right, because for example if you flashed firmware for a similar device with different video hardware your display would stop working.
Sorry to be bearer of bad news, but everything you've shown points to that being what you've got.