Firefox works like a charm! One must be careful which addons one installs into it and how to use it in that case, though... Also, not all websites are compatible with FF. Sometimes one needs Vivaldi, Opera etc. to get a thing done => like Royal Mail tracking, for instance, didn't work at my end in FF. So, open it in Vivaldi and do it... Not all coders are equally good, not all websites are compatible with all browsers...
I noticed last night that Firefox nightly has vertical tabs so I switched to it. It is more stable then Zen and they look similar when vertical tabs are activated.