Avoid them. You may see experimental builds of LineageOS 15.1 (Android 8.1) or 16.0 (Android 9) for SM-T280. In practice:
The Spreadtrum drivers were never fully updated, making higher Android versions unusable as daily drivers. samsung galaxy tab a6 smt280 custom rom best
This is widely considered the most stable and smoothest experience for the T280. Avoid them
Recommendation: Do not use this. The performance trade-off is not worth the API level upgrade. The Spreadtrum drivers were never fully updated, making