[COPIED]
The Olympedia mix'n'match catalog is available at https://mix-n-match.toolforge.org/#/catalog/4628. Particularly via https://mix-n-match.toolforge.org/#/list/4628/auto, users can review suggestions and add missing Olympedia identifiers to Wikidata items via "Confirm", or reject the suggestion via "Remove". There is plenty to do, and still many easy cases to process.
The data (identifier, name, country, discipline) was scraped from Olympedia itself. It currently contains all listed 2020 Summer Olympics participants (11882 in total) except for Hockey players which are currently not available from Olympedia due to a bug. If necessary, I will update the catalog since there are still updates on Olympedia's side.