ingredients = db.Column("ingredients", db.Text)

If you want a normalized database then Ingredients should be in a different table/tables.

categories = db.Column("categories", db.Text)

The categories most definitely should have an m-to-n relation with the recipes.

rating = db.Column("rating", db.Integer)

Who is rating the recipe and how? Shouldn't the rating be tied to the person rating it? And if so, you need to have a mapping table that contains user_id, recipe_id and rating.

image = db.Column("image", db.Text)

There can be only 1 image per recipe?

class Categories(db.Model):

What is this table doing? And why is there no relational linking between this and the Ingredients table?

The categories are rather hard to browse as they are in a really small font - there also seems to be some issue with certain names

I think in this case it should be one category but the rendering issue is also there for other categories

When randomly checking through different pages on the home page there seem to be some issues with redirects:

Here you seem to have some issues with redirects (likely not caused by you)

Additional note - I think you should at least provide a link to where the recipes come from?

Hi. You should remove that debug=True from the app call because the app is in production. Refer to this document from the Flask documentation.

Clicking the search button with no text in the search box will cause a URL Not Found Error.

Also I would recommend adding a button or some way to get back to the home page.
On the recipes page, the "Go to back to recipes." link isn't working. And when on a search page there is no way back to the home page.

When trying to access a "fake" ID the site should fail gracefully e.g. when accessing some random id