The phrase "although not popular" is correct and usable in written English.
It can be used to introduce a contrast or exception regarding the popularity of a subject or idea.
Example: "The theory is considered groundbreaking, although not popular among mainstream scientists."
Alternatives: "despite its unpopularity" or "even if it's not widely accepted".
Although not popular with moviegoers, it earned some critical praise.
Although not popular in Britain, the French eat about 4,000 tons of frogs' legs a year, equivalent to 60-80 million frogs.
Although not popular with all residents, communication between the force and those on the streets is said to have dramatically improved.
Although not popular in North America, Cricket has an audience in the billions with fanatical support across the former British Empire.
Although not popular in feature selection literature, perhaps the simplest way to understand discriminatory nature of feature in a training set with two classes can be by using a search using naive bayes classifier.
Prescribed burns, although not popular, Flannigan said, can do wonders.
Although libertarianism was not popular among 19th-century philosophers, it enjoyed a revival in the mid-20th century.
Although vouchers are not popular with all Republicans, particularly those who moved to the suburbs for better schools, they are strongly supported by low-income African-Americans whose children attend poor-quality city schools.
Although it is not popular as an outdoor PBR, there is potential to develop it as an indoor PBR with artificial light.
Although he was not popular during much of his political career, Israelis have built up a deep affection for him that has been widely expressed during nearly six years as Israel's president.
The settlers brought Shinto and Buddhism religions to the islands, although they were not popular with indigenous people.
