The phrase "are mainly served" is correct and usable in written English.
It can be used when discussing the primary way in which something is provided or delivered, often in the context of food, services, or products.
Example: "In this restaurant, vegetarian options are mainly served during lunch hours."
Alternatives: "are primarily offered" or "are chiefly provided".
Poorer residents are mainly served by buses, if at all, says Daniel Chatman of the University of California, Berkeley, who studies regional planning.
In IaaS model, infrastructure requests are mainly served by allocating the VMs to cloud users [2].
Expatriates in Oman are mainly served by the private health care system, because the majority of them work in the private sector [ 3].
The impact of this policy and the role of expatriates who are mainly served by an expanding private health care sector in relation to TB control have not been previously explored in Oman.
Gyoza dumplings are mainly served with a soy based tare sauce, which you can season with rice vinegar.
Many of the city's restaurants and hotels are beginning the slow process of reopening -- like Alex Patout's, above, which was a cause for celebration -- but they are mainly serving recovery workers and residents who are returning to inspect what remains of their homes.
The lyrics, such as they are, mainly serve as instructions to the musicians, Stubblefield being prime among them: "You don't have to do no soloing, brother, just keep what you got … Don't turn it loose, 'cause it's a mother".
In Europe and South America, pumpkin is mainly served as a vegetable and used interchangeably with other winter squashes.
This magnificent mountain is mainly served by a couple of cable cars and a big gondola, the Bochard.
Outside China, which accounts for half of global demand and production and is mainly served by local firms, six vast international firms Buzzi, Cemex, Heidelberg, Holcim, Italcementi and Lafarge together have 40% or so of the market.
A 50-nm Mo metal layer is mainly served as a bottom contacting electrode for PFM characterization.
