Install Angular Language server

Run:

npm install -g @angular/language-service@next typescript  @angular/language-server

Adjust lsp-clients-angular-language-server-command to point to the correct locations:

(setq lsp-clients-angular-language-server-command
  '("node"
    "/usr/lib/node_modules/@angular/language-server"
    "--ngProbeLocations"
    "/usr/lib/node_modules"
    "--tsProbeLocations"
    "/usr/lib/node_modules"
    "--stdio"))