Sky Sports claim that Everton have lined up the 26-year-old German as the successor to Leighton Baines, who has struggled with injury problems in recent seasons.
However, it would seem that Leicester are also keen on signing Plattenhardt to provide competition for the promising Ben Chilwell, with 32-year-old Premier League winning left-back Christian Fuchs considered past his best.
The Foxes have already pipped the Toffees to the signing of Norwich City starlet James Maddison, and could aim to follow up that coup by beating the Toffees to the signing of Plattenhardt, who is currently playing for Germany at the World Cup in Russia.
Claude Puel's side have already signed Porto right-back Ricardo Pereira, West Brom defender Jonny Evans and now Maddison, taking their spending this summer to around the £50m mark as the Foxes look to improve on last season's league finish of 9th.
Everton, meanwhile, are looking to boost their squad as Marco Silva, alongside new director of football Marcel Brands, look to overhaul the playing staff. Last season was a disappointing one for the club, finishing eighth despite spending around £150m the previous summer in an attempt to challenge for Champions League qualification.
Plattenhardt has made 108 Bundesliga appearances for Hertha Berlin since joining the club from FC Nurnberg. The defender made his international debut for Germany in 2017 and made his first appearance in a major tournament during Sunday's 1-0 defeat to Mexico.