Digital.
Physical.
Official raws.
The mangaka has made statements recently stressing over fan translations and asking everyone to read on the official site.
I don't want to get into it, largely because I don't want anyone trying to argue with Igarashi about piracy. Igarashi doesn't speak English and no matter how well-intentioned you are it's likely to come across as harassment. I don't think Igarashi was being especially condemning, it was more of an emotional appeal, but with volume 2 coming out in a week it's a stressful time for sales and Igarashi hasn't had the easiest time lately.
If you are ever going to speak to a mangaka saying you're a foreigner and huge fan,
please for the love of god say you MTL it on your own and don't bring up piracy. It's good to be passionate, I'm sure many appreciate the praise, but be mindful about that kind of thing. Japan does not take piracy lightly and it stresses authors out worldwide.