Hello,

This is the error:

ERROR in ./node_modules/ol-ext/interaction/Transform.js 15:0-44
Module not found: Error: Can't resolve '../util/element' in 'F:\React projects\xvi.ker-fakataszter\webapp\node_modules\ol-ext\interaction'
Did you mean 'element.js'?
BREAKING CHANGE: The request '../util/element' failed to resolve only because it was resolved as fully specified
(probably because the origin is strict EcmaScript Module, e. g. a module with javascript mimetype, a '.mjs' file, or a '.js' file where the package.json contains '"type": "module"').
The extension in the request is mandatory for it to be fully specified.
Add the extension to the request.

I fixed the error like this:
in node_modules/ol-ext/interaction/Transform.js

I replaced this line:
import ol_ext_element from '../util/element'
with this one:
import ol_ext_element from '../util/element.js'

Best regards,
Asrat