It seems that in Firefox many extensions don't work with Quantum and most of the new ones are not compatible with the older versions of Firefox (like AdBlocks, link redirect control and other general security ones). Not to mention that you have less and less accessibility to security and privacy preferences from the options menu.
Google Chrome keeps hiding some of its developer tuning settings, which is annoying and to some you don't have access to anymore.
Most of the stocks for the Opera browser were sold to corporations in China, and some Opera updates, contradict past ones (like the removal and re-appearance of the in-built VPN option for instance).
Edge - it still works to download other browsers, so all is well here.
Maxthon changed too - it might be a bit faster but they added ads and a profile, which is a bit annoying.
I haven't yet tried Midori, but I might soon. Currently no browser I have used can give me the protection I need, but truthfully, a browser is generally made for browsing, it is our fault that we want to browse "safely".