There are no reports of LTIR that I have seen however every Oiler's sports source has documented Neal's battle with COVID and his return to play. A google search will show this to be true. When he did return he was never the same.
The Oilers need to investigate this channel of "the long term effects of COVID-19 on James Neal and his ability to perform at the NHL level," if they are not already currently doing so.
They need to be discussing it with league authorities, multiple medical authorities and professionals who are in the know about the human immune system, virologists as well as lung and heart specialists.
If they fail to explore this avenue they place the team at a disadvantage and are ineffective at competing with the other NHL teams.