The World Game understands Shrewsbury Town and Portsmouth are among the admirers of the 24-year-old right back or right midfielder.
Millar has impressed at Newcastle after he joined the club from the Central Coast Mariners in 2019. Last season the former Melbourne City junior made 24 appearances for the Jets, scoring four goals and setting up three others.
Millar is eligible for a British passport and with the uncertainty around the new collective bargaining agreement for the next A-League season, or when the new campaign kicks off, a loan spell or permanent move may be the right option.
It is believed Shrewsbury Town boss Sam Rickets is a friend of Newcastle head coach Carl Robinson, with the pair having played together for Wales for several years.
Millar, who made his A-League debut with the Mariners, told The World Game a move to England appeals.
“The sort of style that’s prevalent in England – the big body, athletic, physical sort of game really matches up well with my characteristics and how I sort of play,” he said.
“I’m really excited to play with the Jets but it’s been a big dream to play over in England, so if an opportunity comes knocking I’m sure the Newcastle Jets would be a bit disappointed but happy to let me go.
“They’ve been a great club so far. Even if something happens they’ll always hold a special place in my footballing journey.”
The new A-League season may not start until 2021, leaving the utility potentially up to four months without any competitive football.
“It’s a very short career and you don’t want to spending three or four months [out] when there’s a massive opportunity to go explore something overseas,” Millar admitted.
“Whether that’s a loan or what, you never know what can happen. There’s still a bit of uncertainty around start dates of the A-League season and when the league will run from and to.
“So I think there is definitely an opportunity with the proposed earliest we’re going to start the season being January, so there’s a three to four month period where you’d love to be playing games.
“That’s how you improve and how you develop – it’s definitely something I’m excited about.”
The Jets have already lost midfielder Dimi Petratos to Saudi Arabian club Al-Wehda and striker Abdiel Arroyo to Israeli club Maccabi Petah Tikva.
Foreigners Wes Hoolahan and Bobby Burns departed earlier this year, while goalkeeper Glen Moss has retired.