i am playing on kongregate, so i am not able to keep my account on desktop version, but there is a temporary trick to keep using flash (i tried it on both edge and chrome) :
-shut down your browser
-go on windows date time settings and disable both auto datetime and autotimezone
-set 1st jan 2021 as system date
-reopen the browser, flash will load
-after flash loaded you can set up again windows auto datetime and timezone
hope it helps, don’t know how long this will work