Unlocked phones only update properly
1. on original carrier ACTIVE sim
2. Samsung Smart Switch app !!!!PC or MAC not the phone app!!!
3. if all else fails go to a Samsung Experience Rep. At a Best Buy or similar and ask them to update it
I have the T-mobile unlocked GS9. I've been with T-mobile since the GS2. I've noticed over the years that it doesn't matter if it's T-mobile locked or unlocked the monthly security updates are usually sent out the following month. I expect the June 1st monthly security update sometime in July, July 1st update sometime in August.
The pattern sometimes varies depending on what's included in the the update. If it contains important app updates and they see app crashes, and other issues then they hold the update until they get all of them resolved. I've seen them hold one or two updates for two months.
I prefer this as opposed to carries the send the June 1st update out on June 5th and watching for all the issues being reported. I see a few posts like this every time. Camera crashes, messenges missing, locked out of phone, bootlooping, ect. I still find myself checking for updates every few days towards the end of the month. It must be a brain freeze or glitch.