If you own a fairly recent official Android TV device, you should probably expect an update to Android TV 9.0 in due time, but for TV boxes running Android instead, I was not aware of any models running Android 9.0 so far.
Having said that, with Android 9.0 support announcements from Amlogic and Rockchip made earlier, we knew Android 9.0 boxes would eventually become reality, and according to listings on Geekbuying, there are at least two Rockchip RK3328 TV boxes running Android Pie: A5X Max going for $45.49 shipped with coupon A5XMAX9, and X88 MAX+ selling for $49.99 including shipping.
- SoC – Rockchip RK3328 quad core Cortex A53 processor @ 1.5 GHz with Mali-450MP2 GPU
- System Memory – 4GB DDR3
- Storage – 32GB eMMC flash + full size SD card slot
- Video Output – HDMI 2.0a port up to 4K @ 60 Hz with HDR support + 3.5mm AV port (composite video)
- Audio Output – HDMI, AV (stereo audio), and coaxial S/PDIF
- Video Codecs – 4K @ 60 Hz decoding for H.264/AVC Base/Main/High/High10 profile @ level 5.1, H.265/HEVC Main/Main10 profile @ level 5.1m and VP9
- Connectivity – 10/100M Ethernet, 802.11 b/g/n WiFi (2.4GHz) and Bluetooth 4.1
- USB – 1x USB 3.0 port, 3x USB 2.0 host ports
- Power Supply – 5V/2.5A
- Dimensions – 115 x 115 x 25 mm
The box ships with a remote control, a power adapter, an HDMI cable, and a user manual.
A5X Max networking options are a bit weak with Fast Ethernet, and single band WiFi, so you may consider spending an extra ~$5 for X88 Max+ if dual band WiFi 5 is important in your environment, and/or want the extra storage. Both boxes come with 10/100M Ethernet. Also note that X88 Max+ has a different set of USB ports with one USB 3.0 port, one USB 2.0 port, and one USB 2.0 type-C port.