Should I ask for a LOR from my future Master's Supervisor? I start my master's year project in mid November this year and am currently applying to graduate school, most of whose deadlines are 1st of December. I was wondering if it was acceptable to ask my master's year supervisor for a letter of recommendation despite not having actually started in the lab yet? For more context, we have interacted twice in person and over video and have been communicating over email. But as a research lab degree I was wondering if it would be too soon to ask my supervisor for a letter, but at the same time wouldn't it appear odd that I haven't submitted a letter from my supervisor for my graduate school applications, especially considering my masters field is very closely linked to what I wish to pursue in graduate school. Also, when would be the best time to ask - once I start in the lab mid Nov for a 1st Dec deadline or just before starting, giving them a bit more time?
EDIT: I'm doing a Master's in the UK and applying to US graduate schools
I would ask them now if they could imagine writing a letter, either now (outlining the reasons why they took you as a student), or close to Dec 1st.  But I would phrase it in a way where it is clear that you don't expect them to do it, since they don't know you well yet.  This way, your prospective supervisor can choose whatever they prefer - either they are happy to do it, or they will tell you that they can't judge you sufficiently well and that you should ask someone else (this is what I would do).
What I wouldn't do is to wait until close to the deadline and ask them then - first, if they say so you have to find someone else within a very short time (and most people don't like this, understandably), and second, this might come across as some kind of blackmailing (&quot;I need your letter, since now it is to late to get someone else's&quot;).
In any case, good luck with your application.
(P.S.: As always, adding context about the country/region in which you are doing your master and in which you are applying can help you to get more tailored answers.)