In the beta, there's currently a bug which changes servers to Objective mode when playing Steam Fortress, as the map defaults to Objective mode.
My suggestion is half-bug-fix, half-QoL: for servers/solo games that default to Survival or Objective, put maps of both types in the map list, with maps that support both modes listed twice with (Survival) or (Objective) following them. AFAIK, servers can customize their map list to show maps of multiple game modes, so the functionality is already at least somewhat there.
Include a server option to enforce the default game mode for those servers who wish to be only Survival or Objective.
My suggestion is half-bug-fix, half-QoL: for servers/solo games that default to Survival or Objective, put maps of both types in the map list, with maps that support both modes listed twice with (Survival) or (Objective) following them. AFAIK, servers can customize their map list to show maps of multiple game modes, so the functionality is already at least somewhat there.
Include a server option to enforce the default game mode for those servers who wish to be only Survival or Objective.