What are some relatively popular alternatives (that are not on the JVM)? Maybe the options are somewhat limited here if you want both to be functional.
It has the drawback of the frontend language not being as tiny as Elm is, but it has the benefit (which I think is no little benefit) of having the same statically typed language (F#) on both front and back end.
Whether it's "Relatively popular" is hard to say. It's tiny as far as web stacks popularity goes, but in completely functional web stacks it probably has taken a bite already.
The JVM is a great kitchen sink environment. The BEAM and Erlang/Elixir are much more finely tuned for their strengths: distributed systems, fault tolerance, immutable data/functional programming.
If you need raw performance, the JVM is definitely better. If you don't want to have to deal with the inherent tension between a FP language and mutable surroundings, the BEAM is worth a look.
It has the drawback of the frontend language not being as tiny as Elm is, but it has the benefit (which I think is no little benefit) of having the same statically typed language (F#) on both front and back end.
Whether it's "Relatively popular" is hard to say. It's tiny as far as web stacks popularity goes, but in completely functional web stacks it probably has taken a bite already.