Updating my iPhone 8 plus
I intend to update my software to iOS 15. But there isn’t a software update option on my iPhone 8 Plus
iPhone 8 Plus, iOS 14
Maybe you need to scroll down more to "S"?
There are different ways to ensure the highest iOS that your device will support is installed on your device.
An iPhone 8 or later will only update to the latest iOS, 16.6
This support article has instructions about updating an iPhone or iPad wirelessly --> Update your iPhone or iPad - Apple Support Read the article for recommended criteria for being able to use wireless updating.
You can also use Mac and PC computers to update system software --> Update iOS on iPhone - Apple Support
If you want a video about doing this, follow this link —> https://www.youtube.com/watch/1FcE86kwODQ
When updating, your device will update to the highest version currently available that it will support, or it will just say it is up to date (and can't go any higher) and won't install anything.