It's not really about that -- most shops don't support the latest version of Opera or Brave except by accident since they're Chromium backed. If they introduced a breaking incompatbility there is very little chance we would carry patches for them.
'supported browsers' are browsers that you lose customers if you don't support. You don't lose customers by telling them to switch to Chrome. Firefox's market share is small and the number of people who exclusively use Firefox and refuse to switch is vanishingly small.
'supported browsers' are browsers that you lose customers if you don't support. You don't lose customers by telling them to switch to Chrome. Firefox's market share is small and the number of people who exclusively use Firefox and refuse to switch is vanishingly small.