Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in Hong Kong. I couldn’t find any coupon for this product on latest product update.
Link: Banggood product page
Price: -3 USD
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): Email5, BGUMIDIGIF2, BGAFF10OFF
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for UMIDIGI F2 6/128GB Global.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).