I've actually worked with a couple of companies who do use GitHub for their code, and they all use Linear in addition to GitHub.
I understand the concern you're talking about wrt. Codeberg, but I wouldn't view it as a significantly bigger risk than anything else. Any platform can suddenly decide that your project is against ToS (GitHub will absolutely not accept just anyone's use of their platform either) and Codeberg introducing some rules recently doesn't, in my mind, drastically increase the risk of a dramatic ToS change in the future. But we all have to make our own risk evaluations and I won't judge yours. Luckily, moving between Git hosts isn't that difficult; setting up CI again and losing merge request history does suck but it's not the end of the world, unlike something like, say, losing your AWS/GCP/whatever account.