I was wrong to say Taiwan has only four major players. There are at least five sizable players: two major ones and three smaller ones.

Taiwan has about 110K taxis in total, and that number includes Uber drivers as well, since they are required to have taxi licenses.

According to media estimates, the two biggest players, 55688 and Uber, each have more than 20K drivers. The three smaller players (Line Taxi, yoxi, and 55178 ) each have around 8K to 15K drivers.

If Bolt is included, that brings the number to at least six competitive players. Bolt is one of the top three ride-hailing companies in the world and has just entered Taiwan.

So the market is really crowded. Personally, in Taiwan I mostly use Line Taxi, and sometimes Uber.