All the nodes of my Hebrew site using Drupal 8 have this problem: The URL of all the nodes of my Hebrew site are similar to htts://www.example.com/he/node/1, instead of https://www.example.com/node/1. The difference is that now URLs contain /he/, which I have never added.
It happens even when a node has its language set to English or Not specified.
What I tried is the following:
I changed all nodes written for English speaking audience from Hebrew to English and I flushed the cache. This didn't help: The URLs still contained /he/.
I thought it could be caused by the Alternative hreflang module, but uninstalling it did not resolve the issue, even after flushing the cache.