Installed unmaintained ports

Is there a way to list all Ports I have installed that don't have a
maintainer?

I'm a bit concerned that genuinely useful Ports are disappearing from the
tree, and wonder if more can be done to encourage new maintainers. I'd also
like to see a "FreeBSD Maintainers Guide" or similar as I found working
with FreeBSD Bugzilla recently extremely non-intuitive. I'm sure this gets
easier with practice but as the maintainer of a single solitary port that
rarely requires updating but which required a distfile URL change recently, I
was completely lost.

Particularly the part where "maintainer-approval" flag must be set to "+"!

Maybe there's a guide somewhere that I've missed.

Anyway, my question is prompted by ftp/axel recently being removed from
Ports. It was erroneously noted that upstream was dead in ports/MOVED:

$ grep axel MOVED | grep 2022
net-p2p/awgg||2022-09-30|Has expired: Depends on expired ftp/axel
ftp/axel||2022-09-30|Has expired: Last release in 2009 and dead upstream, please consider using www/aria2

However a quick web search shows the project is still alive:

https://github.com/axel-download-accelerator/axel

Another reason given was the port lacks HTTPS support:

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=263905

But should that matter? That seems like an arbitrary reason for removal.
Anyway, it's also not true of recent versions.

Is dead upstream sufficient reason to remove a port? I'm listed as the
maintainer of editors/uemacs. The source code is now 26 years old! The
author, Daniel M. Lawrence, died in 2010.

(IIRC the only reason I'm listed as maintainer of editors/uemacs is because
I submitted a trivial patch for it to continue builing with Clang when
FreeBSD stopped using GCC.)

Regards
Andrew