The only browsers that even seem to work are Chrome based; Firefox doesn't appear in the debugger selection list even though it is listed in the list of supported browsers.
I'm not sure what to do; this is really frustrating. At times I really wonder why I'm paying for an all tools subscription with half the functionality never works or is broken.
 One thing that I have discovered is that this seems to be related to Live Editing. I just discovered that if I turn live editing OFF I can now launch and connect to the browser, albeit without the ability to Live Edit changes in the browser.
Any help or suggestions greatly appreciated.
Using Google Chrome: Version 86.0.4240.111 (Official Build) (x86_64) and Vivaldi 3.4.2066.86 (Stable channel) (x86_64)
IntelliJ IDEA 2020.2.3 (Ultimate Edition)
Build #IU-202.7660.26, built on October 6, 2020
Runtime version: 11.0.8+10-b944.34 x86_64
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
GC: ParNew, ConcurrentMarkSweep
Non-Bundled Plugins: Scratch, Shifter, com.arasthel.groovy.override-completion, GenerateSerialVersionUID, VisualVMLauncher, com.hartmanster.compareToGenerator, soapUI Plugin, com.paperetto.dash, nl.jworks.intellij.bootstrap3, org.jetbrains.plugins.rest, mobi.hsz.idea.gitignore, org.jetbrains.plugins.vagrant, org.sonarlint.idea, de.dm.intellij.maven-archetypes-catalog-plugin, com.dmarcotte.handlebars, com.intellij.react.css.modules, org.jetbrains.kotlin, com.intellij.plugins.html.instantEditing, izhangzhihao.rainbow.brackets, Pythonid, DeepBugsPython, net.ashald.envfile, ru.adelf.idea.dotenv