Yes it’s possible to publish the widget in a product page from the liquid file however it's not recommended.
From Ongoing ➡ Getting Started ➡ click Publish Snippets.
Please note Shopify does not recommend publishing the widget from the liquid file as Shopify will be deprecating this by January 2024, so we wouldn’t recommend this path as it will be unsupported by all Shopify subscription apps.
Shopify has transitioned to using app blocks with 2.0 themes which can be added & edited via the Shopify theme builder.
We recommend using a Shopify 2.0 themes which are fully supported (Shopify offers many beautiful free 2.0 themes as well that work amazing with Ongoing subscriptions, I’ll link my favorites here )
Why using an official 2.0 Shopify Theme is recommended:
Shopify no longer supports vintage themes
All updates for Shopify subscriptions apps are made for 2.0 Themes
Ongoing supports all 2.0 Shopify Themes
If you purchase an official 2.0 Shopify theme on the Shopify Theme Store, you get free upgrades to all new versions of the theme, including the 2.0 version!
If you already purchased an official Shopify PRO theme, follow our guide here on how to preview how your website will look with the 2.0 version
All new updates in Shopify for subscriptions are made for 2.0 Shopify themes
Shopify is requiring all Shopify Themes on their Shopify Theme store to be 2.0
If there’s any way we can help you with this or if you have any questions, please let us know!