How do you handle international taxation for subscription apps?

I have a Flutter app with Razorpay payments charging $10/month. I need to add sales tax/VAT based on user location but I'm confused about the implementation. For my home country (India) I know I need to add 18% GST. But what about users in the US, EU, UK, Canada, etc? Do I need to register for tax in every country? At what revenue threshold do you typically start worrying about this? I see small SaaS products handle this somehow. Do you just charge tax in your home country initially and ignore the rest? Use a service like Paddle or Merchant of Record? What's the simplest approach when starting out? Would appreciate hearing from anyone who's implemented this.