Today I upgraded the Bash language server (to v3.0.3), after which I noticed that it stopped working. When loading a .bash file, the language server didn’t load and told me to look in the error output for more information. In Emacs, the errors of the Bash language server can be found in the *bash-ls::stderr* buffer, which showed me: 

/home/lennart/.emacs.d/.cache/lsp/npm/bash-language-server/lib/node_modules/bash-language-server/node_modules/vscode-jsonrpc/lib/common/linkedMap.js:40
        return this._head?.value;
                          ^

SyntaxError: Unexpected token '.'
    at wrapSafe (internal/modules/cjs/loader.js:915:16)
    at Module._compile (internal/modules/cjs/loader.js:963:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)
    at Module.load (internal/modules/cjs/loader.js:863:32)
    at Function.Module._load (internal/modules/cjs/loader.js:708:14)
    at Module.require (internal/modules/cjs/loader.js:887:19)
    at require (internal/modules/cjs/helpers.js:74:18)
    at Object.<anonymous> (/home/lennart/.emacs.d/.cache/lsp/npm/bash-language-server/lib/node_modules/bash-language-server/node_modules/vscode-jsonrpc/lib/common/api.js:37:21)
    at Module._compile (internal/modules/cjs/loader.js:999:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1027:10)

I re-ran lsp-install-server, which pointed out that I had nodejs v12.22.5 installed and the language server required v14 or higher.

Time to figure out how to install a newer nodejs version on my Ubuntu 21.10 machine. It turns out that v12 is no longer maintained. The current LTS version of nodejs is v16. Here I found instructions on how to install a given version of nodejs on Ubuntu. For v16, this boils down to running 

curl -sL https://deb.nodesource.com/setup_16.x | sudo bash -

The script that this command fetches (and executes as root) is quite elaborate, but in the end it simply creates the file /etc/apt/sources.list.d/nodesource.list, with the following contents: 

deb [signed-by=/usr/share/keyrings/nodesource.gpg] https://deb.nodesource.com/node_16.x impish main
deb-src [signed-by=/usr/share/keyrings/nodesource.gpg] https://deb.nodesource.com/node_16.x impish main

After that, a simple apt upgrade didn’t suffice. The nodejs upgrade was held back because of a dependency problem. Even an explicit upgrade of the nodejs package didn’t work: 

$ sudo apt upgrade nodejs
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Calculating upgrade... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 libnode72 : Conflicts: nodejs-legacy
E: Broken packages

So, I resorted to a full apt dist-upgrade, which worked fine. After that, I reopened a Bash script and all was fine.

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