Open System Preferences, General, and return it to Light Mode so you can see what you're doing. If you can't read the text of the Installer, that's probably because you're in Dark Mode in Mojave. You will need a free account for the download link to work. Make the thumb drive a bootable Installer disk for macOS Mojave All these 3 steps are essential for successful installation. The Format should be macOS Extended (Journaled) and you should be able to choose Scheme in GUID Partition Format. From the left list of devices, make sure you select your actual thumb drive device, and not its partition.When on Disk Utility, click the View menu from the top menu bar, and click on Show All Devices.Plug your USB thumb drive on a USB 2.0 port, and from the Spotlight, type Disk Utility and press Enter.Make sure you copy the Installer to the Applications folder before continuing.

You need a free account there for download links to work.

If your Mac is too old to support Mojave, download Mojave from Olarila here.

Once downloaded into your Applications folder (leave it there) right-click on the Installer's icon on the Dock and click on Quit.

Wait a few seconds until it asks you if you are sure you want to download Mojave.

This will open the Software Update Preferences pane.

Click on the View button on the macOS Mojave, and click on Get.

Open the App Store on a Mac that supports the macOS Mojave (I used my Mac Mini for this), and type macOS Mojave on the Search bar, and press Enter.If you have data on your thumb drive, now is the time to back them up somewhere else, as this process will delete everything on the disk.Prepare the USB thumb drive and download macOS Mojave

Macos mojave for bootable usb