There is no such thing as "Bitcoin Core" as an organization.

Yes, there are from time to time scam posts or some nonsense pull requests by people who don't know how to use GitHub properly.

It's not FOSS, you don't code stuff for self-love or fun, you implement what manager orders you to, what is in the plan. Have heard that in Microsoft if you work on software A, but decide to improve something in software B, management people of B will likely reject that change, as they don't want to deal with your stuff, that's not for what they are being paid.

What are "Core coins"?

Have MikroTik router at home. Main Internet is wired connection. But MikroTik's also have USB port, where you can plug in either external USB storage for LAN access or LTE modem. And I had some old Huawey LTE USB modems laying around, so have that mobile broadband as a backup Internet.

Just do it!

I like how at some parts of Grīziņkalns neighborhood in Rīga the old style street lights are restored.

If you want to build packages from the source optimized for your machine, why not just use Gentoo Linux?