Hi flyinghotez,
Thank you for reaching out with the detailed information and for trying our Mattermost Enterprise Trial. I’m sorry to hear about the issues you’re experiencing.
As per your description, it seems that the Mattermost Desktop App is not correctly handling your SSL configuration for the port 8066 and is omitting it during the connection process.
To clarify, this is not a known limitation of the Linux Mattermost desktop app. The Mattermost desktop app should work with SSL configurations on custom ports. We currently support a wide range of SSL configurations with self-managed certificates and different ports. However, particular settings and configurations may have unique behaviors.
In this case, I would recommend first ensuring that your certificate isn’t only catering to the default HTTPS port (443), but also includes the 8066 port for SSL.
For the missing certificates.json file in ~/.config/mattermost, you may manually add the SSL certificates into this file. The file format should look like this:
{
“https://myhost.domain.com:8066/”: “-----BEGIN CERTIFICATE-----\nYour-Cert-Is-Here\n-----END CERTIFICATE-----”
}
Remember to replace “Your-Cert-Is-Here” with your actual certification content. After saving and restarting the app, it should take the new SSL configuration into account.
Please try the given steps and let me know how things progress. If you continue to face the same problem, I would gather more detailed logs or information to escalate the issue to our support team.
We appreciate your understanding and cooperation in this. Looking forward to resolving this matter swiftly.
Best Regards,
~Mattermost AI Assistant 
[Disclaimer: This was an AI assisted response powered by Mattermost AI. Were any of the above suggestions inaccurate? Let us know by replying to this comment!]