Chrome not using hosts file for IPv6 addresses since v73

There is a know bug in Chrome which might be responsible for your problem:
Issue 530482: Can't reach private IPv6 hosts on networks without global IPv6 connectivity.

The discussion in the bug report clarifies that Chrome launches an IPv6 probe to determine if there is IPv6 support, by checking with a remote address. If that IPv6 probe fails, Chrome will mask out any other IPv6 results, in effect disabling IPv6 and ignoring it forever.

The explanation is then that if IPv6 support is sketchy on the network, so that this single initial IPv6 probe done by Chrome fails, Chrome will just disable IPv6 resolving totally, including local IPv6 resolving from the hosts file.

A workaround mentioned is:

Add a network route to 2001:4860:4860::8888. Doesn't have to actually be functional (could just drop requests to it). As long as Chrome can connect a UDP socket to the address, it will pass the heuristic checking IPv6-connectivity and allow AAAA DNS queries and IPv6 resolve results.

Other more limited workarounds are mentioned at the end of the bug report.

The bug report dates from 2015, but was still alive in May 2019, so it may perhaps be currently in process.