inundated by ads on iPhone. how do i stop them?

You're going to need to be more specific. Do you mean ads on websites? If so download a content blocker like Adguard.

Controversial opinion maybe, but: pay for your apps/subscriptions. The makers need to feed their families as well. If you don’t want to pay big corporate, or the app doesn’t offer an ad-free alternative, switch to an indie alternative instead. If you can, pay for a lifetime plan.

I would recommend, at a minimum, two things:

1. NextDNS
2. AdGuard for iOS

Once you have those set up and working, if you're feeling adventurous, try:

3. StopTheMadness for iOS (costs $10)

Just NextDNS will block a lot of stuff, as long as you're not on a VPN (Using a VPN will switch to the VPN's DNS servers). AdGuard takes a little more work to set up, since you have to enable content blockers, but it's not too hard as long as you carefully read and follow the instructions in the app. The 3rd thing is a lot more involved, but it adds a last little bit of protection in the browser.

Edit: somebody suggested pi-hole, which is fine, but it's redundant with NextDNS and pi-hole would only work while you were on your home wifi.

If you're on iOS 14 or higher, you can natively use a service that blocks ads via Encrypted DNS.

Sign up for NextDNS and create an adblocking profile. Then follow the set up instructions.

I uninstall apps from my phone that have ads that prevent the experience from being decent. I understand then need for ads but if you force me to regularly watch 30 second ads? You’re gone.

Pixel + GrapheneOS

Let's you just outright firewall apps from the internet, plus opens you up to all the FOSS apps.

If you have time, an old pc and want a project for the weekend, you can setup a pihole, which is a network-wide adblocker. A.k.a it will block ads on any device that's connected to your home wifi.

I usually use Mullvad with ad blocking turned on