I need iOS and iPadOS. Although ideally there’d be a GUI that could work on all of the “mainstream” OSes, since most of my problem here is that I frequently need to move files between devices in different walled or unwalled gardens.

For desktop PCs, Rymdport (formerly wormhole-gui) may be suitable. It's cross-platform with pre-built binaries for FreeBSD, Linux, macOS and Windows on x86-64 and arm64:

https://github.com/Jacalz/rymdport