How do you get references without alerting management?

Ask before you need it. "Hey Tina, if I were to move jobs in couple years, would you be a reference?"

But I also wonder why you care - is it so that you can keep your job if you don't get the new offer?

You can't. At least in infosec the managers at the place you are applying to will call up your current manager and as many of your coworkers as they can about you. The last place I interviewed at, even before the interview random coworkers were asking me about it.

In tech in general "you have no privacy" especially applies to job hunting.

It is dirty and trashy but apparently only some states have it illegal.

References are for HR, hiring managers and back-channel chatter are something else. YMMV.

The hard case is moving from your first IT job.

Look for references outside your employer.

Way back in the mainframe days, we were running compiles and tests down the street at another insurance company. Their data center manager gave me a reference.

Customers and vendors are good.

Once in your second job, you can use previous managers and co-workers.

There were a few employers that called me back to help out in my spare time which I was happy to do.

Only ask people to be your reference if you would trust them with things like not alerting management.

I don’t use my current manager as a reference, only former managers.

i quit a fortune 50 without notice. they kept paying me for a month to try to get me to come back. never went back. all of my managers still gave me a good reference at my next fortune 50. i have fuck you money, so, ymmv.