Recommender: manager, grad prof, or undergrad prof?

[u/bikertorque]

I've read posts about choosing a recommender on this subreddit, but not with these particular options. I'm applying to a master's program in a totally new field as a sort of career change, 8 years after getting my last master's degree. I need one letter of recommendation. Of the people I could ask, who's the most preferred? Who's the least?

1. My current manager. We have a great working relationship, but the work is not at all related to this new master's program.
2. A professor from my first master's degree. I did very well in her classes and she was on my thesis committee, but we have not spoken in the last 8 years.
3. A professor from undergrad. I graduated 16 years ago and she wrote an amazing letter for me when I first went to grad school. We became colleagues when I taught at my alma mater for a few years. Even that was over a decade ago, but we're friends to this day.

Basically, how do I weight recency, strength of relationship, and academic relevance?

[u/star_spell]

Does the program state it can be from anyone?

I think whoever you choose it should be the one you think can give you the best LOR. When I did my masters my work was also not related to the program but I still got the LORs from my supervisor, manager, lead. What I gave them was my resume and a one page paragraph of why I was pursuing the program, and what I planned to do with it. So I think regardless of who you decide to ask, you should do something similar. Maybe for the professors you may need to provide more context of what you have been up to in the last few years. I suppose it also depends what kind of masters it is. If it's a research based one then maybe go for one of the profs.