We do not recommend or support lazyloading comments.
Google has said that it will not index anything hidden behind a click/interaction on page, so if you have to "click to load more comments", those comments will not be indexed.
This is a significant SEO problem, because comments contribute to your main content, and you can rank for keywords found in comments even if it's not in the content.
Lazyloading comments on scroll is a huge usability problem if someone is trying to access the footer, or even the sidebar on mobile.
In the web.dev 2020 summit, one of the developers said that the footer (or sidebar) should be removed when lazyloading-on-scroll is in place in order to prevent CLS issues.
And avoid page-experience penalties due to poor user experience.
Right now, it looks like paginating comments is still the best method.