Tips

Quote all path variables, or whitespace will make this script explode horribly.
do not depend on cmake directly
Don't align backslashes.
Add indent to followup lines to make continuation stand out.
Per the policy, systemd services are to be installed unconditionally.
:= on all libs you're linking to, to enforce rebuilds when SOVERSION changes.
test deps go into test?, with IUSE=test and RESTRICT="!test? ( test)" in ebuild.
All uses of Python must go through one of python-* eclasses, as documented on wiki.gentoo.org/wiki/Project:Python/Eclasses

The DOCS variable has a default value (see eclass documentation). Meaning that things like DOCS=( README.md ) are usually not necessary.
Try to avoid having a "." or a white space at the end of DESCRIPTION
No symlinks in the repository please. I understand why you would want to do this, however there are some very good reasons no to do this: https://forums.gentoo.org/viewtopic-p-8202534.html?sid=290d68129893b7435e6ecf9c528171a
If you have optional dependencies you might want to use the optfeature function from eutils.eclass instead of elog. I haven't changed this in the ebuild, because it is not strictly necessary
f some of the tests from your package are not working, it is considered good practice to not remove support for tests from the ebuild completely. Instead add RESTRICT="test" to your ebuild to disable the test phase. This makes it easier to re-enable tests in the future, since all the dependencies and functions are still there, you just have to remove the RESTRICT="test" line.

From Andrew Ammerlaan's GURU review

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