My forum stays on the loading screen "Could not find module `virtual-dom` "

Product Support Self-hosting
2

See this in the javascript console:

loader.js:247 Uncaught Error: Could not find module `virtual-dom` imported from `discourse/global-compat`
    at loader.js:247:1
    at u (loader.js:258:1)
    at a.findDeps (loader.js:168:1)
    at u (loader.js:262:1)
    at a.findDeps (loader.js:168:1)
    at u (loader.js:262:1)
    at requireModule (loader.js:24:1)
    at HTMLDocument.<anonymous> (start-app.js:4:15)
    at discourse-boot.js:20:12
    at discourse-boot.js:1:1