This happens to me, too. I'm trying to use it on WSL 2 on Windows, if that helps.

The language server does not crash on the native Windows (but the compiler refused to run there with a rejected promise that I can't reproduce anymore, so taking WSL out of the picture wasn't an option either). In both cases, the version of the extension I installed was 2.5.3 from the VS Code Marketplace.

VS Code 1.55.1 (Edit: same behaviour also in 1.55.2) (Edit, again: also in VS Code Insiders 1.56.0)
Node (in WSL) 14.16.0
vscode-imba 2.5.3

i have the same scenario:
i'm running ubuntu on wsl2 and the imba plugin does not crash when i run vscode from a windows shell vs. a linux shell.

vscode is a windows binary whether launched from a windows shell or a linux shell.
the most salient difference is that, when run from a linux shell, vscode uses the remote wsl extension to run commands, extensions, a terminal, etc. on the linux distro.

i wonder if there is some interaction between the imba extension and the remote wsl extension?

whatever it is, it appears to have caused a syntax error in the index.js file that's part of the imba extension.

For me it happens both when starting VS Code from the Windows start menu, and from the WSL shell.
When I connect to the WSL remote, open the WSL folder and open an imba file, VS code complains that the language server crashed 5 times.

The syntax error seems to be related to the Node version, as the file only throws the error when I execute it with the node binary bundled in the VS Code server:

# With system Node.JS (14.16.1)
~/dev/repro$ /usr/bin/node ~/.vscode-server/extensions/scrimba.vsimba-2.5.3/server/index.js
# Throws an error related to a missing file, but not a syntax error
# Probably because I didn't give it the right arguments or environment from the command line

~/dev/repro$ ~/.vscode-server/bin/08a217c4d27a02a5bcde898fd7981bda5b49391b/node ~/.vscode-server/extensions/scrimba.vsimba-2.5.3/server/index.js
# ...snip...
SyntaxError: Unexpected token '?'
    at wrapSafe (internal/modules/cjs/loader.js:1053:16)
    at Module._compile (internal/modules/cjs/loader.js:1101:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1157:10)
    at Module.load (internal/modules/cjs/loader.js:985:32)
    at Function.Module._load (internal/modules/cjs/loader.js:878:14)
    at Module.require (internal/modules/cjs/loader.js:1025:19)
    at require (internal/modules/cjs/helpers.js:72:18)
    at Object.<anonymous> (/home/seb/.vscode-server/extensions/scrimba.vsimba-2.5.3/server/index.js:1:1)
    at Module._compile (internal/modules/cjs/loader.js:1137:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1157:10)

As the node version bundled with the server should be the same that is bundled in the desktop VS Code, I now wonder why I don't see a syntax error on Windows? 🤔

I dug deeper and found that the language server runs after running the server/dist/src/index.js file through babel to eliminate the ?? and ?. operators, using @babel/plugin-proposal-nullish-coalescing-operator and @babel/plugin-proposal-optional-chaining.

I ran the following in the server/dist/src/ directory and reloaded the VS code window afterwards:

~/.vscode-server-insiders/extensions/scrimba.vsimba-2.5.3/server/dist/src$ mv index.js index.js.orig && babel --plugins "@babel/plugin-proposal-nullish-coalescing-operator,@babel/plugin-proposal-optional-chaining" --filename index.js < index.js.orig > index.js

good work braunse!
is it feasible for me to make manual changes on my local machine to fix this problem?
i assume i would be making these changes to files that are part of the imba extension?