Although "with prefix_term" may still grab "Xiaomi Redmi 8A" or "Xiaomi Redmi 8T" when searching "Xiaomi Redmi 8". You will need to experiment, and if that setting still does not work then look at modifying the ProductLoadAllPages stored procedure, around line 77 you could try removing the * so the prefix behavior is ignored (or just comment out the BEGIN to END).
IF @FullTextMode = 0
--0 - using CONTAINS with <prefix_term>
SET @Keywords = ' "' + @Keywords + '*" '
With Full Text disabled, go down to line 138 and remove the + '%' after @Keywords, or comment the line out for an exact exact match.
--usual search by PATINDEX
SET @Keywords = '%' + @Keywords + '%'