Some of my favorite communities that are fun and active are:

• !bicycles@lemmy.ca
• !cyberpunk@lemmy.villa-straylight.social
• !foss@beehaw.org
• !games@sh.itjust.works
• !linux_gaming@lemmy.ml
• !steamdeck@sopuli.xyz
• !technology@lemmy.world

r/RedditAlternatives is another one that might be worth mentioning instances on.

I recommend Waistline if you use Android. It’s on F-Droid.

The barcode scanner uses a community run database (Open Food Facts) for nutrition facts so you might find that you need to manually input items or correct outdated info more often than compared to the more popular My Fitness Pal. Obviously that gets easier once you build up a collection of your usual foods in the app.