When researching your question, I found several websites with information about growing winter aconite but very little about killing it. Digging it is the preferred method of control, but, as you said, you must lift the entire clump and remove all of the tubers. This is the most effective method when done properly and will do the least amount of harm to your landscape.

Although I did not find any remedies specific to winter aconite, a non-specific or broad leaf herbicide should be effective. And, as you mentioned, the problem with this is containing the damage as other desirable plants will also be susceptible.

The rule of thumb is to start with the least harmful methods and move up the intensity as needed. With that in mind, here is a link to home brewed solutions that can be quite effective.

5 Homemade Weed Killers That Really Work (thespruce.com)

Another thought is to investigate natural weed killers. I have had luck with a product that is basically concentrated vinegar. You can see some options on the website below. There are many other options and I am not recommending any one in particular.

6 Best Weed Killers (2024 Guide) - This Old House

A general herbicide such as glyphosphate will certainly work but you could well be left with large dead spots that won’t regrow for some time.

It might be helpful to learn a little about winter aconite before you tackle this. All parts of the plant are toxic and could be very dangerous to children or pets. Read about it here:

Winter Aconite, Eranthis hyemalis – Wisconsin Horticulture