Hello, why am I receiving an empty array with just let { data: categories, error } = await supabase .from('categories') .select('*')

This would be hard for anyone to guess since we don't know your system setup. Maybe you don't have any data in that table, maybe your RLS isn't configured properly.

Setting API keys as

service_role

+

secret

resolved my problem. Thank you

If this is on the client side please don't do it. Exposing those keys on the client means that someone can do real harm to your data. I think your issue is related to row level security (RLS).