Use Mattermost Desktop with SOCKS5 proxy [Ubuntu 20.04]

[P9k]

I would like to use the Mattermost Desktop app on Ubuntu 20.04 via a SOCKS5 proxy (established with SSH) to access a Mattermost instance running within an internal network.

With Firefox, everything works fine following these steps:

1. In a terminal, establish the SOCKS5 proxy with ssh -D 8080 remote-server-in-internal-network
2. In Firefox, I activate the proxy settings: 'Manual configuration' -> SOCKS5 (with localhost and port 8080) + Usage of SOCKS5 proxy to resolve DNS requests
3. In a new tab, I can access the Mattermost instance under https://internal-domain-for-mattermost (Mattermost server is set up to re-route from port 8085 to port 443)

However, using the Mattermost app does allow me to access the instance when using the internal domain https://internal-domain. It says that the address could not be found although Firefox can resolve it just fine.

Starting the Mattermost app with --proxy-server="socks5://127.0.0.1:8080" or --proxy-server="socks5h://127.0.0.1:8080" has the outcomes.

I suspect that the DNS is not resolved via the SOCKS5 proxy the same way Firefox is able to. Also, I have experimented a bit and found that Chromium can resolve the DNS request via SOCKS5 when called with --proxy-server="socks5h://127.0.0.1:8080".

Can you advise how I can get the Mattermost Linux app to resolve DNS via a SOCKS5 proxy? :-)

Many thanks in advance!!

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A bit more background: Using the server's IP directly does not work for me: I have to use https://internal-domain-for-mattermost since another web service (a wiki) is running on port 443 of the server (under a different internal domain). Depending on the used domain name it is possible to choose which one should be called.