I have the following comments and suggestions:
1. Add a link to the upstream pull request or commit from which you took the patch.
2. consider adding a `Requires: systemd >= 243`, in case this spec gets reused for older releases
3. you can save yourself the manual flag export by using the `%set_build_flags` macro
4. please link directly to the spec file in raw form and preferably via a stable URL (as mentioned in https://bugzilla.redhat.com/show_bug.cgi?id=1795399#c1)

Please fix 1 and 2, 3 is optional but I would highly recommend it for the future as %{optflags} is actually a legacy macro (the new one is %{build_cflags}). Then I'll approve this package. And thanks for resurrecting it!


Package Review
==============

Legend:
[x] = Pass, [!] = Fail, [-] = Not applicable, [?] = Not evaluated
[ ] = Manual review needed


Issues:
=======
- Package does not use a name that already exists.
  Note: A package with this name already exists. Please check
  https://src.fedoraproject.org/rpms/brightnessctl
  See: https://docs.fedoraproject.org/en-US/packaging-
  guidelines/Naming/#_conflicting_package_names


===== MUST items =====

C/C++:
[x]: Package does not contain kernel modules.
[x]: Package contains no static executables.
[x]: If your application is a C or C++ application you must list a
     BuildRequires against gcc, gcc-c++ or clang.
[x]: Package does not contain any libtool archives (.la)
[x]: Rpath absent or only used for internal libs.

Generic:
[x]: Package is licensed with an open-source compatible license and meets
     other legal requirements as defined in the legal section of Packaging
     Guidelines.
[x]: License field in the package spec file matches the actual license.
     Note: Checking patched sources after %prep for licenses. Licenses
     found: "Unknown or generated", "Expat License". 5 files have unknown
     license. Detailed output of licensecheck in /home/dan/fedora-
     scm/review-brightnessctl/licensecheck.txt
[x]: License file installed when any subpackage combination is installed.
[x]: %build honors applicable compiler flags or justifies otherwise.
[x]: Package contains no bundled libraries without FPC exception.
[x]: Changelog in prescribed format.
[x]: Sources contain only permissible code or content.
[-]: Package contains desktop file if it is a GUI application.
[-]: Development files must be in a -devel package
[x]: Package uses nothing in %doc for runtime.
[x]: Package consistently uses macros (instead of hard-coded directory
     names).
[x]: Package is named according to the Package Naming Guidelines.
[x]: Package does not generate any conflict.
[x]: Package obeys FHS, except libexecdir and /usr/target.
[x]: If the package is a rename of another package, proper Obsoletes and
     Provides are present.
[x]: Requires correct, justified where necessary.
[x]: Spec file is legible and written in American English.
[-]: Package contains systemd file(s) if in need.
[x]: Useful -debuginfo package or justification otherwise.
[x]: Package is not known to require an ExcludeArch tag.
[x]: Large documentation must go in a -doc subpackage. Large could be size
     (~1MB) or number of files.
     Note: Documentation size is 10240 bytes in 1 files.
[x]: Package complies to the Packaging Guidelines
[x]: Package successfully compiles and builds into binary rpms on at least
     one supported primary architecture.
[x]: Package installs properly.
[x]: Rpmlint is run on all rpms the build produces.
     Note: No rpmlint messages.
[x]: If (and only if) the source package includes the text of the
     license(s) in its own file, then that file, containing the text of the
     license(s) for the package is included in %license.
[x]: Package requires other packages for directories it uses.
[x]: Package must own all directories that it creates.
[x]: Package does not own files or directories owned by other packages.
[x]: Package uses either %{buildroot} or $RPM_BUILD_ROOT
[x]: Package does not run rm -rf %{buildroot} (or $RPM_BUILD_ROOT) at the
     beginning of %install.
[x]: Macros in Summary, %description expandable at SRPM build time.
[x]: Dist tag is present.
[x]: Package does not contain duplicates in %files.
[x]: Permissions on files are set properly.
[x]: Package must not depend on deprecated() packages.
[x]: Package use %makeinstall only when make install DESTDIR=... doesn't
     work.
[x]: Package is named using only allowed ASCII characters.
[x]: Package is not relocatable.
[x]: Sources used to build the package match the upstream source, as
     provided in the spec URL.
[x]: Spec file name must match the spec package %{name}, in the format
     %{name}.spec.
[x]: File names are valid UTF-8.
[x]: Packages must not store files under /srv, /opt or /usr/local

===== SHOULD items =====

Generic:
[-]: If the source package does not include license text(s) as a separate
     file from upstream, the packager SHOULD query upstream to include it.
[x]: Final provides and requires are sane (see attachments).
[x]: Package functions as described.
[x]: Latest version is packaged.
[x]: Package does not include license text files separate from upstream.
[!]: Patches link to upstream bugs/comments/lists or are otherwise
     justified.
[-]: Sources are verified with gpgverify first in %prep if upstream
     publishes signatures.
     Note: gpgverify is not used.
[-]: Description and summary sections in the package spec file contains
     translations for supported Non-English languages, if available.
[x]: Package should compile and build into binary rpms on all supported
     architectures.
[-]: %check is present and all tests pass.
[x]: Packages should try to preserve timestamps of original installed
     files.
[x]: Reviewer should test that the package builds in mock.
[x]: Buildroot is not present
[x]: Package has no %clean section with rm -rf %{buildroot} (or
     $RPM_BUILD_ROOT)
[x]: No file requires outside of /etc, /bin, /sbin, /usr/bin, /usr/sbin.
[x]: Fully versioned dependency in subpackages if applicable.
[x]: Packager, Vendor, PreReq, Copyright tags should not be in spec file
[x]: Sources can be downloaded from URI in Source: tag
[x]: SourceX is a working URL.
[x]: Spec use %global instead of %define unless justified.

===== EXTRA items =====

Generic:
[x]: Rpmlint is run on debuginfo package(s).
     Note: No rpmlint messages.
[x]: Rpmlint is run on all installed packages.
     Note: There are rpmlint messages (see attachment).
[x]: Large data in /usr/share should live in a noarch subpackage if package
     is arched.
[x]: Spec file according to URL is the same as in SRPM.

Thanks a lot for the review!

(In reply to dan.cermak from comment #1)
> I have the following comments and suggestions:
> 1. Add a link to the upstream pull request or commit from which you took the
> patch.
Done!

> 2. consider adding a `Requires: systemd >= 243`, in case this spec gets
> reused for older releases
Great idea, done!

> 3. you can save yourself the manual flag export by using the
> `%set_build_flags` macro
Cool, learn something new every day.

> 4. please link directly to the spec file in raw form and preferably via a
> stable URL (as mentioned in
> https://bugzilla.redhat.com/show_bug.cgi?id=1795399#c1)

Spec URL: https://raw.githubusercontent.com/gicmo/spec/63e0fdb4cf814de0a0f3d10c87ae8f96c58ed61a/brightnessctl/brightnessctl.spec
Scratch build: https://koji.fedoraproject.org/koji/taskinfo?taskID=41217160

LGTM now, package approved! Thank you for bringing brightnessctl back!

*** Bug 1778512 has been marked as a duplicate of this bug. ***