About a year ago, there were several topics (like this) in this community about enabling data sever mode in Brave. These suggestions were rejected due to privacy concerns and the fact that adblocker and tracking protection themselves do save a lot of traffic.
But there is another technique that does not require any third-party servers. You just tell websites that you wish to save traffic by sending them a
'Save-Data: on' HTTP request header. I found out about this in a blog post by Daniel Aleksandersen (I am not him, just sharing an interesting idea) and installed his extension for Firefox (source code available here).
This technique works only for sites that support it, but while the original Chromium Data Saver is removed in Brave, why not replacing it with an alternative one?