There is no future for maintenance. Judging from the current basic situation, the after-sales of big brands tend to be vertical.
Then how to develop as an individual really needs a certain vision. The technology is really good. It is possible to find one or two or even more brands to do after-sales service, and it is even possible to get them to sign a contract with you. However, the things under warranty are really not fun. If the customer service is not good, the manufacturer will punish you and you will never get the money. Kung fu is beyond poetry, and the final income of maintenance is earned outside the warranty period.