Apart from using Puffin Browser (or some other way to run an in-browser Flash), no, sorry.

what happened to migrating to HTML5 so we could use browsers again?

 Plarium said in 2018 it decided against HTML5

Then we got an unexpected surprise notice from Plarium in dec 2019 that they were working on HTML5 after all and it was just taking longer than expected.. 

I do not think this is important anymore since those remaining are used to Plarium play by now.

Just curious.

As a player, I heard that they got some version working, but not well enough (whatever that means), so they decided to stick with the app as long as it works and the majority of the players are happy (in the widest possible sense, i.e., they are not leaving). Don't know how much truth there is in that.

As a mod, all I know is that HTML5 is not happening any time soon.