The manager and the company are one and the same. The manager is an agent of the company. A company cannot do this and expect GDPR not to cover it.
Companies can farm publicly available data if they want, but it is subject to GDPR, although the consent side is slightly different. There still needs to be a lawful use of that data (six categories available in article 6). The closest the manager could argue would be a "legitimate interest" for the company to collect and use that information (article 6 1.f).
https://gdpr.eu/article-6-how-to-process-personal-data-legally/
https://gdpr.eu/Recital-47-Overriding-legitimate-interest/
That would be really difficult to argue in my opinion.
In this case, this isn't public data anyway but information only available to the manager in a private capacity. So the consent side of this blows everything away anyway.