I would say that an airline will avoid hiring an applicant that is not assessed as eventual "captain material". It's not the maximum return on the airline's investment.
An applicant would never say in an interview that they only wanted to be a lifelong FO, except under special circumstances like an older hire who is likely to retire before meeting the experience requirements, or someone who has limiting medical conditions at hire (like the Type 1 diabetics who are now flying in some countries) that prevent them from qualifying for PIC.
An FO has to apply to upgrade to captain, so theoretically, someone can continue as an FO indefinitely (in a union operation at least), up to a point, but I think it would be career suicide to say so up front during the interviews.
It does happen though. An acquaintance of mine some years back was still copilot at a major airline, flying heavies, with somewhere around 25 years in. He finally upgraded to captain for the last years of his career. One of his motivations was he'd gotten to the point of being at the top of the seniority ladder for copilots.
He was making way less than he would as captain, but he didn't care about the money so much, and was more interested in the bidding benefits of being top of the heap in his "junior" heap in bidding for pairings, insofar as he got the best routes and the best schedules and the most time off. Upgrading to capt would mean he had to drop to smaller aircraft and a lower rung on the seniority ladder(back to working over Christmas, etc), and temporarily less money . He finally upgraded to capt more or less in response to management and peer pressure in his later years (he said at the time).
There are a number of websites that post interview Gouges ("gouge" is a slang word for intel reports on an airline's recruiting/interview practices) like here. These can give a good sense of the kind characteristics they are looking for, and you will never find one that advises people to state that they don't want to progress to captain.