That should be fine, I was on an s9 and it was pretty solid on that. Sorry you are running into issues! (Keep that note 9 as long as possible, I still miss the lack of expandable storage and having a headphone jack on my device)
I find it strange that you're having this issue. I haven't had this issue on my OnePlus 3T, Note9, or Pixel 7 Pro using Fennec F-Droid or Mull (FOSS forks of Firefox)
It's not a website issue, but a browser issue, that seems to be related to switching between multi-tasking. From the looks of things, either the browser or the OS kills the page, which then doesn't resume properly for some reason.