Here is a solution that I found, after quite a lot of struggle…
I had, in my tsconfig.app.json, under the CompilerOptions tag
"types": [
"node"
]
After Installing @types/webgl2, I did not add it to tsconfig.app.json, so Angular could not find the WebGL2RenderingContext declaration.
All I had to do is install @types/webgl2 with npm, and put the following in my tsconfig.app.json, onder the CompilerOptions tag:
"types": [
"node",
"webgl2"
]
Now it seem to work ok.