I'm doing something similar with [1] where pagination (scroll down, click on "Show more") is implemented by requesting the next page as an HTML fragment from the server, loading it into an invisible iframe and once it finished loading, appending it to the current page.
We used to let people browse and page through photo galleries by preloading the next columns or rows of photos, then on click URL swapping under the static HTML page grid. The order you replace the URLs gives a visual of a paging motion.
And for infinite pages, a long forgotten technique: for scrolling or continuing content, you could use "multipart" since the 90s, effectively streaming the additional page content to the user as you got more bytes to send them.
[1] https://animasci.com/