Yes, certainly, but all of these, if they want to sync their data, or use a own selfhosted server or have to use those of Mozilla with an account, giving with it datas to Alphabet (Google) and googleanalytics. Sync is essential if you use the browser in several PC, PC and Mobile or simply as backup if the PC fails or you buy a new one and don't want to lose your bookmarks, passwords and other data. Forks are a lot out there, also very nice ones, but most of these lacks the basic infrastructure, depending on a lot of third party services. A browser isn't only an app to surf the web, it's a continuos work, maintance, servers and most important, a good and active community. How many forks offer all this? There are almost 100 different browsers out there and other 70 which had said Game over for us, from people which thought "Nice, its easy to fork this engine making it to my like and gain a lot of customers", nice short dream with a product oversaturated in the market.