Same. I never had it in writing, but spoken contract. I'd wait til after negotiations and 'one more thing' them.

Two companies didn't care at all. One did - the worst it ever got was asking me to boot up their supplied Windows laptop once a month for updates, so they could pass security audits.

I am surprised; why is this your policy? I am sure you have a good reason, but I can't guess what it might be.

My approach is exactly the opposite: I never do anything work-related on personal hardware, nor do I ever use work machines for personal projects.

Same, but Redhat was oddly okay with me using fedora.