Preventing things from launching at boot/login?

OK, I know about login items, what I want to stop is not there.

Microsoft (gack) Update and Tailscale both launch on a restart. Can’t find where to prevent this. I’m sure it was covered on Day 1 of Mac User School (which I took decades ago) but I can’t figure it out.

Call me a noob if it helps, but I’m stuck. Sequoia 15.7.9 on an Intel iMac & Apple silicon MBP.

PS: This is my 4th MBP and my 2nd iMac.