I agree with the rsgain recommendation. In my search for a ReplayGain utility, I had tried MusicBrainz Picard (flatpak), which uses rsgain as its backend for ReplayGain. I found Picard to be somewhat cumbersome, though. I just wanted a simple utility.
Unfortunately, Linux Mint 21.3 (my distro) does not meet the dependencies for the current version of rsgain's deb package. I would need to compile it from source.
Being relatively new to Linux, and not trained in computing, I had hoped for a GUI application (rsgain is command line only), but I've been dipping my toe into the command line more and more, so I waded in a little further -- and with rsgain's excellent instructions, I was able to successfully compile and install the program!
It's a steeper learning curve, to be sure, but once I figured out how to tweak the configuration, I was able to achieve scan results identical to what I had generated using MusicBee or foobar2000.
I think rsgain will be my go-to for volume normalization. Thanks for the recommendation!