If Java versions can coexist on a system
If all java versions have their own packages on the AUR
If you can change envvars in a launch script and be sure that all processes of the application will persist your settings
Then why THE FUCK do package maintainers keep announcing to change the default java version to install their package, rather than explicitly doing that by themselves? Fuck off, do you really think yours is the only package that needs a specific Java version? Do you think each and every user will write their own init script, or edit the PKGBUILD to include the new version as an envvar in the desktop file? This is why Arch has a bad name, and they're fucking right. If you don't have the time to put a single motherfucking diff in the motherfucking pkgbuild to specify the java version in the desktop file, then don't fucking maintain the package. I know there are too few maintainers, but pretending to maintain a package while doing fuckall is much worse than leaving it unmaintained on the AUR so the first person who has time can pick it up.

The positive side of EnvVars...
So a couple of weeks ago I moved all api keys and db passwords to environmental variables on the server so that I didn't have to keep worrying if I'm live in my test environment.

Earlier I shat myself after an apt-get upgrade broke php and apache somehow decided it's a great idea to serve all .php files as plain text. I was super relieved to find no confidential information (apart from logic) was made public.

Docker compose switches users but doesn't update the home directory. Both switching users and not touching envvars are very sensible default behavior, but the result is that the running service has no write access to $HOME - and many programs don't provide sensible error messages for this rather unlikely scenario.

Is there anything like React Context or Unix envvars in any functional language?

Not global mutable state, but variables with a global identity that I can set to a value for the duration of a function call to influence the behavior of all deeply nested functions that reference the same variable without having to acknowledge them.