The user @tasism tried to post the following reply, but for whatever reason the forum software does not let me approve his post. Therefore posting manually:
As I stumbled upon this thread trying to get to get the kopano-docker setup to work behind my reverse TLS proxy (haproxy, not nginx), I just wanted to share the required configuration changes that allowed this to happen for me:
First of all, the configuration variable has changed its name in later versions and is now SECURE_COOKIES (not INSECURE_COOKIES). I chose to put the following in the kopano_webapp.env file:
KCCONF_WEBAPP_SECURE_COOKIES=false
In addition, I commented out the FQDNCLEANED variable in the .env file:
#FQDNCLEANED=....
That’s it, very easy from this perspective…