ImHex Looks amazing, but I couldn't get it to work on my system last time I tried. Not a pre built version and not compiling it myself. So I wrote myself a simple hex viewer. Only a viewer, don't need an editor. All other hex editors that I could get to work on my system where really disappointing. Either they couldn't handle large files (>2GB), or they lacked features, like decoding the bytes at the current location as various integer types, had very cumbersome controls for navigation, or displayed important information like the current offset in uneditable labels (status bar) and even didn't give it enough room for large files so it got cut off! Did they never use their own program? Anyway, my viewer only has a terminal interface, so you can always select and copy any text it displays. Also has IMHO handy controls to jump around to absolute and relative offsets. See: https://github.com/panzi/rust-hox
But don't look at the ugly code. I just cobbled it together somehow because I needed exactly that.
Your software seems to be in the same vein as hexyl. I can't personally vouch for how well it handles large files cause it's been a while, but I suspect it'll do alright.