In a recent interview, members of Kubrat Pulev's team had mentioned Croatia as a possible location for the mandatory fight with IBF, IBO, WBA, WBO heavyweight champion Anthony Joshua.
Initially scheduled for June 20 in London, the fight was pushed back due to the coronavirus pandemic.
There was talking of July 25, but that's not going to happen - as Joshua-Pulev is a fight that's not likely to take place behind closed doors.
"We have about three more weeks left on the exploring and then we'll see where the best options lie," Pulev's manager Ivaylo Gotsev told Sky Sports.
Hearn is still hoping to stage the fight in the UK, before a crowd, before the end of the year.
The British Boxing Board of Control is targeting July for the return of boxing in the UK - but fans will not be allowed to attend the events - and there is no telling how long that protocol will stay in place.
If the 'closed doors' mandate remains in place beyond the summer, Hearn is very willing to take that fight abroad.
"The focus remains the same - do the fight in the UK. We have also now conceded that AJ will only fight once this year. Before it was all about getting that fight in early-August to make sure we could fight in December. Because of the preparation needed and the magnitude of his shows, AJ will only box once in 2020," Hearn told Sky Sports.
"We hope between September and December live gates will return to the UK. There is also a chance they won't - if that's the case, we will take the fight elsewhere.
"We have had a number of approaches from the Middle East, China, and Croatia to stage the fight. We want to give ourselves every opportunity to stage it in the UK but we know it may not be possible. We want the mandatory defence boxed off, out of the way, before he moves into the undisputed fight next year."