Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (389.99 USD): BGabf1b4
(CouponsFromChina.com tip: coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGJUNEGSG9, DealBGimpact, Cuponation9, BG03728a, BGJPMNR5, BGMNTBR5C, BgGoodie9, BG8ReviTrage, BGb3b3e7, BGc2be0f, BG8OFFCOUPON, TTBLACK5, BG05b35a, BG4a6598, JanBGCoupon8, BGSaleFeb8, BGSaleAD
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for T-BAO R5 Ryzen 5 5600U 16/512GB Mini PC.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).