Most of the first links above recommend an Epsom salts soak first as well. The Tricide Neo is an alternate treatment for those who have done the other things.
Another third method is to use Tricide Neo soaking. Read the posts by @dawg53 here:
https://www.backyardchickens.com/threads/how-i-cured-bumblefoot-with-tricide-neo.1283554/
And here another link about the product:
https://ouroneacrefarm.com/2013/11/09/bumblefoot-treatment-tricideneo/
A link...
I usually go ahead and do the surgery to avoid the soaking and other methods, but you can try to soak and use the non-surgical approach as well. Here are a few links to read:
https://www.tillysnest.com/2015/12/non-surgical-bumblefoot-treatment-html/...