Elliott is a private equity fund. They own more Windstream debt than anyone else (they bought much of it at a steep discount). They shake up and restructure troubled companies.
They bought a stake in AT&T in 2019, then sent its board a letter telling them they were doing a poor job and "suggesting" changes.
Here's an article written at the time:
https://www.fiercewireless.com/wireless/elliott-trashes-at-t-management-and-its-execution-wireless
Here's a link to the letter:
https://www.businesswire.com/news/home/20190909005482/en/Elliott-Management-Sends-Letter-Board-Directors-ATT
It's long but clear and worth a 5-minute skim, if for nothing else than the section headings. I'd say it's a harsh but fair and accurate picture of AT&T's problems.
I can imagine the letter they might write for Windstream.
The Elliott people are smart and hard-nosed. As the biggest creditors and biggest future shareholders, they will call the shots on who runs the company going forward.