Not sure how much weight this really has in a market such as mobile phones in which additional external competitors are never going to become a reality.
And that's one that got big enough to remember them. Wikipedia lists 188 mobile phone manufacturers [1]. A lot of them very local (e.g. EvertekTunisie making phones for Tunisia and Morocco) or defunct; But even my local (German) retailer offers 35 brands. Big ones like Apple, Samsung and Xiaomi, budget brands like Oppo or ZTE, niche brands like CAT or Beafon. It's a crowded market that doesn't seem particularly hard to enter.
And judging by the spotty compatibility of LineageOS they don't all use the same hardware either.
1: https://en.wikipedia.org/wiki/Category:Mobile_phone_manufact...