Reading the posts in some of the offered links, I found one that gave a path to a Mac OS setting = Privacy and Security, then Local Network. Then turn the Brave Button on to access other devices.
I might have seen that setting earlier, but it didn’t register because the only other browser in the list was FireFox. There was no entry for Safari or Opera (both of which work with the NAS).
I know I didn’t turn that option OFF, so it was either a “gift” action from OS 15.4, or there was something in that update that required more attention to Brave than before.
This issue is resolved for me.