I decided that the app was getting stable enough that I wanted to try if I could convince others to join. I switched to VPS hosting, which decimated the loading time. I switched to a Postgres database.
Next was optimizing my signup procedure. Before this, my "landing page" was just a login and a signup button, no description or anything. So I had to write marketing texts. Not my strong suit, especially how to summarize in a few words what the app does (mostly for English users) and why it's better than existing options (for Dutch users).
I also had to actually create a register button. Before this I had to manually create accounts. I had to create the entire workflow, captcha protection, what fields are required, email verification etc.
Next was finding users. I soon figured out that there was much more competition than I had counted on for such a niche app. I assumed that eetlijst was my main competitor, but there is also monipal, wiemee, and many others competing for such a small niche, all much more established and streamlined.
Marketing for such a niche audience is difficult. I try speaking to any fellow students I catch using a competitor, but usually they say "Oh, we always used this, and I'm not responsible". That is the challenge of marketing an app meant for groups and not individuals.
So I tried online marketing. Typing behind my computer is much more my forte, in fact I'm doing it right now. Submitted my app to every directory and showcase that would handle it. I had no budget, my app doesn't even have any monetization right now. However, I think it is probably too niche for this approach. The biggest competitor has 5K downloads on their mobile app. The chance that anybody in the target category will be among the maybe 5 random visitors a day is astronomically small.