galaxy 8+ won't upgrade because it can't find wi-fi

No wifi no updates

 

If your phone only has Verizon's cellular connectivity and you have no WiFi network available, your phone should automatically opt to use mobile data when there's no WiFi connection. If you're typically leaving mobile data disabled to save data usage or for whatever reason, try going to a place with a public WiFi network. Local libraries, community colleges, and a lot of restaurants/bars are common places for free WiFi. Keep in mind that those public sources are also hazardous as far as online security so use them for things like receiving OTA updates but be very, very judicious about also things like online banking, or anything that involves you logging into account using a password.

 

Mobile data is just that, hence the name mobile data. Turn your Wi-Fi off.
In your phone settings.

 

Something to keep in mind is you don't get to determine which version of the Android operating system for your phone, that's something that the phone manufacturer (in your case Samsung) and your chosen carrier (Verizon) will determine for you, and when it's convenient for them to do so. And that's a big variable as some phones get more upgraded promptly, some after a few months, and some will never be upgraded. A lot of people mistakenly equate upgrading smartphones with PCs where the user has more options and control over system upgrades and updates but they are two very different platforms.
Which version of Android is your S8 + currently running and what version do you want to upgrade to?

If you've been using your phone to go online, apps works and you can browse web sites, you're already using mobile data (your Verizon cellular account service). So upgrades will be applied whenever Verizon releases S8 + upgrades to you. If you're already using the most current version that Verizon is offering, don't bother trying to force your phone to upgrade, it just doesn't work like that. You have the option to root your phone and then apply a corresponding third-party firmware for your S8 + that may be more current, but that's not a trivial task so be sure to research thoroughly and double-check every step you do. (...and be absolutely sure you have all your data backed up, and don't just assume your backup solution is working. Check that your data is accessible and restorable).
On the chance you're mixing upgrade and update terminology, Verizon does publish an update schedule for their phones. Apparently your phone should have at least the August update patch:
https://www.verizon.com/support/sam...&mboxSession=405a71d9d92247d080500f71d1616041

 

You can use Mobile Data

 

If you're not connecting your phone to a local WiFi network and your cellular connection is the only way you want to have online access, it is using up some battery power for no reason. When you go into your Settings >> Wi-Fi menu, there should be an option to toggle the WiFI off and on. Enable it just for those times you do need it.Or is it matter where you do leave it disabled and there's some app that keeps switching on?

 

But also there should be an option in "settings" then to "more mobile networks" where your phone chooses mobile data over Wi-Fi data..the default is Wi-Fi data..

I swear I've seen an additional option somewhere..

Ohh yes there's another one inside the Google ps settings..
I hope any of the advices listed helped..