You are right, Inter is the most serious team to bring Lukaku they make every effort to get this player we don't know what the reason but maybe because Inter has no other choice and Lukaku is considered cheap and can be relied on. The rumors are Inter ready to release 6 players in order to secure Lukaku so we can imagine how important Lukaku for Inter even though the performance wasn't very good last season.
Inter need Lukaku up front. and last season Lukaku played quite well with the team. that is the reason why Inter are after Lukaku who was previously on loan. moreover Inter also lost several players in their main squad. so Inter must quickly finalize Lukaku's transfer which has been hampered by price negotiations with Chelsea. even with the addition of several players offered by Inter, it might still not be what Chelsea hopes for.
Lukaku himself refuses to play at an Arab club that is willing to pay dearly. and emphasized that he wanted to play for Inter Milan. I think Inter can do their best to bring Lukaku back.