Letter of recommendation from employer I have worked as a mobile dev in a small creative software company for a year, and I'm preparing to apply for CS masters in US as an international student (for AI-related field).

Question: Do you think it's good idea to use a letter from my employer? 

I only have one strong letter from my senior project supervisor and I can't find another strong (and personal) one from my undergrad university since I've never really been close with the rest of faculties.

I think having one letter that talks about me personally (like work ethics) would be great. With this I'd have 2 letters from professors (1 strong, 1 generic), and 1 letter from my employer.

However, I've heard that it's not recommended to use a letter from someone not in academia, especially someone who's not in the field I'm applying to (more like in business). My current job title is also not related to AI at all, as I'm doing mobile app development.

I'm thinking that since I graduated last year, and didn't have nice projects to show in my portfolio, the letter from employer will at least demonstrate the work, or fill the gap of what I've done in the past year.

Thanks for reading! Any suggestion is welcomed.
Yes, get the letter from your employer. In general, people reading letters want to see assessments of your skills, work ethic, etc., and these can certainly be provided by someone not in academia. Certainly if all aspects of content were equal, it would probably be more useful to get a letter from an academic, since it would likely map more directly onto likely success in Ph.D. research, but a strong and meaningful letter from your employer beats a weak and generic letter from a professor.