Making the minimal required upgrades for this to our support matrix would look like this:
'Chrome >= 49',
'ChromeAndroid >= 49',
'Edge >= 79', # drop EdgeHTML
'Firefox >= 52',
'FirefoxAndroid >= 68',
'iOS >= 10', # was 9.3 — Proxy needs 10
'Opera >= 67',
'Safari >= 11.1',
'Samsung >= 5', # was 4
'UCAndroid >= 12.12',
'QQAndroid >= 10.4',
This would drop about 0.08% of browsers in use by devices that have pinged back in the last year.