Hi,

The instructions on https://www.devuan.org/os/documentation … evuan.html say to download the 'SHA256SUMS.txt' file, in the previous section of the instructions.

You appear to have skipped this step, and that's why the error was received when trying to verify the ISO image; the SHA256SUMS.txt file was not present, as it needed to be, when you tried.

Section 'Check the integrity of images' instructs the user to "Download the SHA256SUMS.txt file".  The following section 'Verify the images' depends on the user having followed the instructions in the former section.

Thanks in any case for reporting the issue, we value our testers and bug reporters.

X.

Brave works fine here.  The best option is to install by adding the Brave repo to sources.list and then install with apt-get.   
Follow the instructions on the Brave web site.  Avoid flatpak, it is bad advice.  Neither are bespoke scripts necessary.  Good luck, and if you have further questions, post here again.  Feel free to let us know if things worked out or not.