When i bought my X98PLUSII i ordered the official keyboard. The big problem is that the tablet has dual Os, and the Teclast keyboard can’t pair with two systems at same time.
Hating this, i bought a Logitech K480, it have a selector for 3 differents devices. The cost is little more expensive, but it’s very good, work much better than Teclast keyboard.
Best portable keyboard I’ve used so far is the Microsoft foldable Bluetooth keyboard. It’s pricy but it has nice key travel, it’s tiny and light and can pair with 2 devices simultaneously.