Hello student. Yes you can. The eligibility criteria to appear for UCEED exam is that the candidate should pass 12th/hsc examination from any board (cbse/state/icse) etc.

Since you are planning to take admission for engineering in 2020, you would have cleared your 12th board in 2020. So yes, you can appear for UCEED 2021

Kindly refer the link for more details

https://design.careers360.com/articles/uceed-eligibility-criteria