Hamburger menu -> Settings -> General -> "Firefox Updates" -> "check for updates but let you choose to install them"
As for losing open tabs, there're a few different extensions that'll allow you to bookmark all open tabs and throw 'em in a folder. Easy enough to do that before updating, then just delete the folder that's created via the bookmarks manager once you've updated/reopened tabs.
Makes sense, considering cryptobros seem to want "get rich easy" and the orange dumpster fire certainly panders to that demographic.