I borrowed an inactive Verizon sim, and did that for my SM-G965U1 S9 plus (on tmobile network), and it worked. But a few caveats to be careful for.
after you pop in the SIM it may not do anything but say 'checking device status' for several minutes. I just kept pressing on the 'Download and Install Updates' button and finally after awhile it said 'checking for updates', and I got the verizon version of the June 1 security patch.
You have to install while you still have the verizon (or other) SIM, if you go back to the tmobile one, it won't work. I had to reinstall the verizon one and repeat the steps and I'm installing as I type now.
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