Sue Gray was well respected at the time across the board for her report. It followed police guidelines as to what was lawful or not: her job was to put together/gather available detailed evidence as part of a team, not alone, and write the report.
At the time she was praised (well, not by Johnson time) for the report, and went back to general Civil Service work under Sunak.
All civil servants have their own political views, but there is no evidence she therefore had bias (if there is, from that time, please produce it). There's a very strict code of conduct on it.
Her choice to leave meant she had the freedom to express her views, as do all civil servants on leaving.
I don't think her skills were suitable for the position she held in the L Party (nor the salary), as we are discussing (and still in the news this lunchtime)
But to attempt to smear her as less than honourable in her role in the Gray report, her previous civil Servant career are unfounded and disingenuous.
She was appointed for the role because of the respect and skills she had, by Sunak, who as people have said is a decent man, and carried it through properly.