The 25-year-old is currently serving a 12-month suspension from all football activity, handed to him by UEFA, after he was found to have the banned substance Furosemide in his urine sample taken in February.
Onana, who insists he accidentally took medication that was prescribed for his wife, has appealed to the Court of Arbitration for Sport and will hear the verdict in June.
According to Goal, Arsenal have been interested in the Cameroon international since January and have previously contacted the player's representatives.
Arsenal's technical director Edu and head coach Mikel Arteta are both admirers of Onana, but due to financial constraints, the club were not prepare to make an offer in the winter transfer window and instead opted to sign Brighton & Hove Albion's Mathew Ryan on loan for the rest of the season.
Onana – who is valued at just £7m, as his contract with Ajax is due to expire in 2022 – has made 20 appearances in the Eredivisie this season, keeping nine clean sheets.