I’m sorry to add to the discussion that you just closed, but one simple option has not been proposed, and I’d like to chime in to add a payment link to the plugin manifest, e.g.:
In plugin.rb:
# frozen_string_literal: true
# name: discourse-example-plugin
# about: A sample plugin to illustrate the simple payment option
# meta_topic_id: 1234567
# version: 1.0.0
# authors: Jane Doe
# url: https://github.com/discourse/discourse-example-plugin
# donate: taler://pay-pull/exchange.demo.taler.net/Z2KC4WB4KYKMYPFY3Q87FQ7MZPPMNV4TXGPQ0DCBT4NXGRY3GEB0
The payment link could be anything that a web browser can understand (e.g., a Stripe link, etc.)