gnidreg wrote:
I am running Mojave and using iTunes with my older devices, but the newer iPhone SE will not work. A dialogue box tells me to upgrade to connect this device.
Per the tech specs, your Mac is fully supported with iPhone SE 3rd.

There’s an update (patch) needed for iTunes (on macOS 10.14 and earlier) and for Finder (on macOS 10.15 and newer) when a new iPhone model meets an old install. This update (patch) is specifically for iTunes or Finder, not for macOS.
If that patch download and installation is not happening transparently and automatically, then reboot into Safe Mode and try connecting again. There can be macOS bugs, and some types of add-on apps can get tangled.
I have noticed the the upper right corner keeps blinking while alternating between SOS only and No Sim. When I was browsing for a solution, people said that nonstop blinking started with IOS 16. They also said it happens if you have a SIM installed and it has stopped working. Anyway, a minor issue. I will just have to learn to ignore it.
Thar’s annoying. If cellular is switched off in control center and cellular data is off, I’d hope it just goes to a solid display. Send some feedback about that: Product Feedback - Apple
I understand the flashing notice if cellular is enabled, but if it’s all been manually disabled, it should be slightly less attention-seeking about it, as is the case with the No SIM shown on the older iPhone I use as an iPod touch is.