Nix is sort of that third option, though I really wish there was a well-documented way to use it on macOS as purely a binary/source package manager. A lot of stuff I read online goes into setting up nix-darwin to manage desktop settings and etc. and I just don't need or want that.
That being said, if you haven't used MacPorts in years, I'd say it's worth the jump. I recall moving from MacPorts in the first place because Homebrew was faster and allowed for customising packages.
When I switched back to MacPorts again, it was because Homebrew had become slow and no longer allowed package customisation. Now, MacPorts is much faster and has the variants system for package customisation.
Thank you for this helpful information. It might be worth a try. I initially moved to brew because it was "new", because I liked the command line interface, and because it seemed more "segregated" from the rest of the OS's files (/usr/local/Cellar and so on). But it's increasingly aggressive messages reminding me I am a second-class (or third-class) citizen due to the age of my OS is really off-putting.
That being said, if you haven't used MacPorts in years, I'd say it's worth the jump. I recall moving from MacPorts in the first place because Homebrew was faster and allowed for customising packages.
When I switched back to MacPorts again, it was because Homebrew had become slow and no longer allowed package customisation. Now, MacPorts is much faster and has the variants system for package customisation.