Sketch Engine does not display the type/token ratio, but it does provide all data necessary for the calculation. They are on the corpus info page (https://www.sketchengine.eu/guide/corpus-info-page/):
The LEXICON SIZES table displays the number of unique items in the corpus.
The COUNTS table displays the total numbers found in the corpus.
The most traditional calculation should be done using words from LEXICON SIZES and tokens from COUNTS like this:
word ÷ tokens × 100 = TTR