Got the issue when running the ionic sample tab app as a browser pwa on iOS.

It also occurs in chrome iOS webview as well as on iphone safari browser.
The bug does not occur on Chrome Desktop or on Android.

The error log from the chrome console;

core.js:9110 ERROR Error: Uncaught (in promise): Error: No available storage method found. Error: No available storage method found. at localforage.js:2743 at ZoneDelegate.invoke (zone-evergreen.js:359) at Object.onInvoke (core.js:34201) at ZoneDelegate.invoke (zone-evergreen.js:358) at Zone.run (zone-evergreen.js:124) at zone-evergreen.js:855 at ZoneDelegate.invokeTask (zone-evergreen.js:391) at Object.onInvokeTask (core.js:34182) at ZoneDelegate.invokeTask (zone-evergreen.js:390) at Zone.runTask (zone-evergreen.js:168) at resolvePromise (zone-evergreen.js:797) at zone-evergreen.js:707 at ionic-storage.js:127 at ZoneDelegate.invoke (zone-evergreen.js:359) at Object.onInvoke (core.js:34201) at ZoneDelegate.invoke (zone-evergreen.js:358) at Zone.run (zone-evergreen.js:124) at zone-evergreen.js:855 at ZoneDelegate.invokeTask (zone-evergreen.js:391) at Object.onInvokeTask (core.js:34182)

app.module.ts

`import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { RouteReuseStrategy } from '@angular/router';
import { IonicModule, IonicRouteStrategy } from '@ionic/angular';
import { SplashScreen } from '@ionic-native/splash-screen/ngx';
import { StatusBar } from '@ionic-native/status-bar/ngx';
import { IonicStorageModule } from '@ionic/storage';
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';

@NgModule({
declarations: [AppComponent],
entryComponents: [],
imports: [BrowserModule, IonicModule.forRoot(), AppRoutingModule,IonicStorageModule.forRoot({
name: '__mystabildb',
driverOrder: ['indexeddb', 'sqlite']
})],
providers: [
StatusBar,
SplashScreen,
{ provide: RouteReuseStrategy, useClass: IonicRouteStrategy }
],
bootstrap: [AppComponent]
})
export class AppModule {}

`
package.json

{ "name": "db-test", "version": "0.0.1", "author": "Ionic Framework", "homepage": "https://ionicframework.com/", "scripts": { "ng": "ng", "start": "ng serve", "build": "ng build", "test": "ng test", "lint": "ng lint", "e2e": "ng e2e" }, "private": true, "dependencies": { "@angular/common": "~8.1.2", "@angular/compiler": "~8.1.2", "@angular/core": "~8.1.2", "@angular/forms": "~8.1.2", "@angular/platform-browser": "~8.1.2", "@angular/platform-browser-dynamic": "~8.1.2", "@angular/router": "~8.1.2", "@ionic-native/core": "^5.0.0", "@ionic-native/splash-screen": "^5.0.0", "@ionic-native/status-bar": "^5.0.0", "@ionic/angular": "^4.7.1", "@ionic/storage": "^2.2.0", "core-js": "^2.5.4", "rxjs": "~6.5.1", "tslib": "^1.9.0", "zone.js": "~0.9.1" }, "devDependencies": { "@angular-devkit/architect": "~0.801.2", "@angular-devkit/build-angular": "~0.801.2", "@angular-devkit/core": "~8.1.2", "@angular-devkit/schematics": "~8.1.2", "@angular/cli": "~8.1.2", "@angular/compiler": "~8.1.2", "@angular/compiler-cli": "~8.1.2", "@angular/language-service": "~8.1.2", "@ionic/angular-toolkit": "~2.0.0", "@types/jasmine": "~3.3.8", "@types/jasminewd2": "~2.0.3", "@types/node": "~8.9.4", "codelyzer": "^5.0.0", "jasmine-core": "~3.4.0", "jasmine-spec-reporter": "~4.2.1", "karma": "~4.1.0", "karma-chrome-launcher": "~2.2.0", "karma-coverage-istanbul-reporter": "~2.0.1", "karma-jasmine": "~2.0.1", "karma-jasmine-html-reporter": "^1.4.0", "protractor": "~5.4.0", "ts-node": "~7.0.0", "tslint": "~5.15.0", "typescript": "~3.4.3" }, "description": "An Ionic project" }

As a workaround we uninstalled ionic-storage and are using dexie.js so far (which works without any problems)