Clone and run npm install, If you wish to update to the latest Ionic delete the node_modules and run below,

ng update @angular/core @angular/cli
npm install @ionic/angular-toolkit@latest

Install the Stripe (cordova) plugin not for Capacitor

ionic cordova plugin add cordova-plugin-stripe
npm install --save @ionic-native/stripe

Ionic Native (peer dependency issue fix)

npm WARN @ionic-native/stripe@5.31.1 requires a peer of @ionic-native/core@^5.1.0 but none is installed. You must install peer dependencies yourself.

You need to install manually as below

npm i @ionic-native/core

Make sure your Ionic project is integrated with Capacitor and not Cordova

npm install cordova-plugin-stripe
npm install @ionic-native/stripe
ionic cap sync

/src/payments/payments.page.ts

  this.stripe.setPublishableKey('pk_test_xxxxxxxxxxx');