I’m just guessing that you have an iPhone, because I have the little update icon showing too. I looked it up, and it’s a major overhaul, so I turned off my automatic updates. If you go to settings and click on the update it takes you to this screen:
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Yours might not say off like mine does. But if you click on the off (or on) you get this screen:
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(Yours might look different now that you’ve updated.)
You can toggle all those to off, and then even if it keeps bugging you to do the update, it will not update until you want to. (I know, too late for this time. But it might help for next time.)
I’m not fond of watching long videos. But I found this one (2 hours!!

) and he systematically goes through all the changes. I’ve been watching it in increments as I feel like it. I have actually found it riveting, and I think once I learn enough about iOS 26, I ought to be able to do the update and not get completely discombobulated.