Setup in nginx will lead to security warning in Google Chrome

Data Mastery asked:

Since 2 days, our users get the following warning when trying to login on our service:

English version:

The information you’re about to submit is not secure

Because this site is using a connection that’s not completely secure, your information will be visible to others.

Send anyway   Go back

This is the setup in nginx we use and which worked for the last 3 years without any issue. It still works, but on Chrome it produces the warning.

   location / {

    proxy_pass          http://shinyproxy:4000; ### Übernahme der servicenamen aus Docker-compose

    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_read_timeout 600s;

    proxy_redirect    off;
    proxy_set_header  Host             $http_host;
    proxy_set_header  X-Real-IP        $remote_addr;
    proxy_set_header  X-Forwarded-For  $proxy_add_x_forwarded_for;
    proxy_set_header  X-Forwarded-Protocol $scheme;
    }

   location /auth/ {
   
    proxy_pass          https://keycloak:8443; ### Übernahme der servicenamen aus Docker-compose

    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_read_timeout 600s;

    proxy_redirect    off;
    proxy_set_header  Host             $http_host;
    proxy_set_header  X-Real-IP        $remote_addr;
    proxy_set_header  X-Forwarded-For  $proxy_add_x_forwarded_for;
    proxy_set_header  X-Forwarded-Proto $scheme;

    }

I found this thread:
https://bugs.chromium.org/p/chromium/issues/detail?id=1158169#c49

This seems to explain it. My knowledge with nginx is only quite basic, but can anyone suggest a workaround here?