27.8.2. oa.com

Tencent owns the oa.com domain since 2020 which they bought from some small early American Internet company, although they don’t announce that clearly on the main domain itself. But they have several subdomains of that being used actively.

On the original company, it stood for "Object Automation" as seen e.g. at https://archive.vn/SsvSV#selection-1123.0-1123.155:

OA is the industry leader and pioneer in the deployment of object-based industrial automation, distributed control, and operational intelligence solutions.

https://domainnamewire.com/author/kasseylee/ mentions that it was sold for $609,068 in 2020, and references https://namebio.com/?s==QjN2UTN1kjM which gives date, value and sale location (https://sedo.com) but not buyer and seller info. https://domainnamewire.com/2020/09/16/why-are-two-letter-domains-so-sought-after-in-china/ says such domains are highly sought after in China.

Subdomain selection: