This sucks. It all looks as though their miner part of the website is down. Worse still, not GitHub to retrieve the older releases from.

I checked out their main site, maybe you can give it a shot by writing to their support

General Inquiries
info@ebang.com

Products Inquiries
products@ebang.com

Edit: from the archived version of the site (https://web.archive.org/web/20210618215111/http://miner.ebang.com.cn/article-13.html) I managed to salvage this;
E-mail：ebit@ebang.com.cn

skype:live:ivy_1434
skype:lynnnesnay
skype:tammyni03

Your best option right now is their support