Deploy a Svelte / Sapper application

Svelte / Sapper deploy
I started to play with Svelte / Sapper as an alternative to Angular.
The development of a simple application is quick and intuitive, I had issues to deploy a small application easily in the cloud.
The solution I found is to create a Docker image of the application and deploy it using Jelastic.
Being the content quite static I exported the result of the original REST answers of the Java backend in JSON files.
Dockerfile
FROM node:14-alpine
WORKDIR /usr/src/app
# the entire project is copied
COPY / ./
RUN npm install
RUN npm run build
CMD ["node", "__sapper__/build"]
EXPOSE 3000
ENV HOST=0.0.0.0
In Jelastic:
I deployed the image behind a NGINX Load Balancer.
Issues
Configuration
The main issue for me was the configuration of different environments: development and 'production'.
In Angular and Java every environment has his own configuration file out of the box.
I didn't find this in Sapper. The solution was to use external plugins. Even changing the port of the server required searching a solution on GitHub (prefix with PORT 80 the starting instruction was the easiest).
Working with different environments and services (backend etc.) it's annoying to don't have a pre-defined solution.
TypeScript
I tried to convert my project in TypeScript, Svelte provides an 'easy migration'. I think the migration failed with Sapper.
I ended using only JavaScript. This is not a blocker for a small project, different story for a big enterprise solution with many developers.
Personal Opinion
I like Svelte a lot. The main project comes with some companion solution for SSR and static website generation that fill some missing features of Angular.
The compilation central idea is a true alternative to React/Vue/Angular. Unfortunately Svelte doesn't seem to receive a lot of interest in the enterprises.