FLAN-UL2
Overview
Flan-UL2 is an encoder decoder model based on the T5 architecture. It uses the same configuration as the UL2 model released earlier last year. 
It was fine tuned using the "Flan" prompt tuning and dataset collection. Similar to Flan-T5,  one can directly use FLAN-UL2 weights without finetuning the model:
According to the original blog here are the notable improvements: