mautrix bridge fails to connect to homeserver in most default config

[hermannsblum]

Playbook Configuration:

My vars.yml file looks like this:

---

matrix_domain: hermannblum.net

matrix_homeserver_implementation: dendrite

matrix_homeserver_generic_secret_key: ''

devture_systemd_docker_base_ipv6_enabled: true

matrix_playbook_reverse_proxy_type: playbook-managed-traefik

postgres_connection_password: ''

matrix_appservice_double_puppet_enabled: true

matrix_client_element_enabled: false

matrix_mautrix_slack_enabled: true

matrix_static_files_container_labels_base_domain_enabled: true

Matrix Server:

• OS: Ubuntu 24.04
• Architecture amd64

Problem description:

I have a problem getting mautrix bridges in a fresh setup to work. This is potentially related to #4182 , who reports a similar issue. I completely reinstalled my server to make sure it is no setup issue and run with the most vanilla config possible. Still, I get the following error in the syslog of mautrix-slack:

Mar 17 18:10:44 ubuntu matrix-mautrix-slack[70957]: 2025-03-17T18:10:44.057Z ERR Failed to connect to homeserver, retrying in 10 seconds... error="failed to GET /_matrix/client/versions: HTTP 404"

Manually checking, there is https://matrix.hermannblum.net/_matrix/client/versions available, but https://hermannblum.net/_matrix/client/versions indeed returns 404, so it seems the bridge does not query the correct subdomain. However, I am not even sure where to configure this? Should this not be the default?

[onestacked]

AFAIK the mautrix bridges only really target synapse homeservers.

[shadshack]

Still an issue.