This looks great! Awesome name too.
Over the past couple of days I have been looking specifically for a chore tracking solution, so it's impeccable timing to see this pop up.
I really like the idea of there not being specific dates or schedules, but just a time since a chore was last done. I've only just set myself up with Grocy last night but tracking things on a specific date/schedule concerns me because sometimes I simply cannot get it done and think the flexibility in what you've gone for is more accommodating.
One thing I would certainly appreciate are notifications on mobile. This doesn't necessarily mean a mobile app (but also doesn't mean not!), but even something that could hook into, for example, Gotify would be neat.
Thanks for sharing your cool project!