Six free PDF sheets, US Letter, no email needed. Each has a section for every part of the meal, a column for how many a dish serves, and a diet and allergen column with a key for vegetarian, vegan, gluten-free, dairy-free, and nut-free, so guests can see which dishes to ask the cook about.
Any gathering
Potluck Sign-Up Sheet
Columns for the dish, how many it serves, and allergens. Tape it up at church, the office, or the kitchen counter and everyone can see what is still needed.
The same sheet works online, free. Share one link and guests claim a dish from their phone, add allergen labels, and see what is still needed. No account for guests, and nobody has to find the clipboard.