My main concern would be graphical user interface compatibility (does it fit on the screen, can you operate the controls with your fingers or do you need the precision of a mouse pointer?)
Command line software should be fine, as long as you don’t mind using an on-screen keyboard.
Of course, it all needs to have been compiled to run on arm64.
Since the RTL-SDR hardware is USB connected, it ought to “just work”.
Individual programs are one thing; it will be considerably more challenging to Install an entire specialist operating system distro, unless the distro maintainers support the Librem 5. I’d rule that option out unless you want to dig deep.