Most companies make you sign agreements which say all IP created during employment is owned by the company. A fair number of companies allow employees to retain IP related to side projects as long as they don't directly compete with the company's products.
Here's my short list : gitlab, stripe, github.
My company makes you preapprove any outside business activities (including freeware/opensource). They ask you stuff like if you are working in the same domain as the company, if you work with any company competitors or clients, etc.
I can't say the name because I am critical of them and need to stay employed.