Checkout UI extensions without Shopify Plus

[Sebastian37]

Is it possible to add a button, with a custom link to the checkout page without the Shopify Plus Plan? Because sadly it's not financially possible for my client to use the Shopify Plus Plan at this moment.

[RobinKZ]

Did you ever find anything out?

I found this in an old newsletter from shopify back in October:
"On October 24, 2023 we will bring checkout extensibility to the thank you and order status pages for Shopify Plus merchants. Basic, Shopify, and Advanced plans will have access by April 30, 2024. Going forward from this date, new merchant shops on these plans will default to extensibility for thank you and order status pages."

But I guess that's not related to Checkout UI? since it has not come to pass.