The Linux file server itself continues to remain online and work well.
What proved less successful was regular interaction with it from a different operating system, macOS.
In principle, macOS and Linux impose few restrictions on file names. However, macOS Finder is less accommodating. Finder won't tolerate file names that contain the colon character. Worse, it won't even acknowledge that they exist.
This proved to be a day-to-day hassle. I was constantly having to "recover" files that I either had given a forbidden name from Linux, or whose names had caused problems when when I migrated them over from HFS Plus (macOS) to begin with.
So, I partially migrated to APFS (macOS). When the warranty expired on my 2012 Mac Mini, I installed a big extra hard drive in it, removed colon characters from all my important files, and copied them back to macOS. Then, I turned on SMB ("Windows") file sharing on my Mac Mini. Problem mostly solved.
I still keep media without DRM, which I consume primary thru Plex, on my Linux box. I also still use my Linux file system for most software development. If I need to keep code in sync with other operating systems, I use git. But I'm careful to use boring file names.
