Adeline, 22, is set to join HSV in the coming days from French side Troyes for a fee of €4m, putting pen to paper on a contract running until 2030. The midfielder is due to undergo a medical on Monday to complete the formalities of the move.
Despite the arrival of a new midfield option, Hamburg are continuing to push for a permanent deal to sign Vieira, 26, from parent club Arsenal, with the two transfer situations said to be unconnected in the eyes of the club's decision-makers.
Sky's report frames Adeline's arrival as one piece of a broader rebuild in midfield rather than a replacement for, or alternative to, a Vieira deal, suggesting HSV see room in the squad for both players regardless of how the Portuguese playmaker's situation resolves.
Vieira spent last season on loan at HSV, contributing seven goals and five assists in 29 Bundesliga appearances as the club secured Bundesliga survival, and his loan deal included a buy option in the region of €20m to €22m.
HSV have been reluctant to meet that figure, instead pushing to renegotiate a fee closer to €10m, a gap that has complicated talks with Arsenal despite both the club and player being keen on a permanent switch.
Vieira's contract at the Emirates runs only until 2027, giving Arsenal an incentive to sell this summer rather than risk losing further value on a player who has fallen well down Mikel Arteta's midfield pecking order.
The dual pursuit underlines the scale of HSV's ambitions in midfield this summer, with the club evidently prepared to add both a lower-cost, long-term prospect in Adeline and a more experienced, higher-profile addition in Vieira if the two deals can be completed in parallel.
Vieira has previously said he would be open to extending his stay in Hamburg regardless of the financial complications, describing the warmth of the club and its supporters as a significant factor in his thinking.