fix(linux): install vendor preset for sunshine-kms service

[psyke83]

Description

• Install vendor preset so that sunshine-kms will default to disabled
• Remove kms service from flatpak and AppImage (as it can't work)
• Small documentation cleanups

Screenshot

Issues Fixed or Closed

Roadmap Issues

Type of Change

• feat: New feature (non-breaking change which adds functionality)
• fix: Bug fix (non-breaking change which fixes an issue)
• docs: Documentation only changes
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semicolons, etc.)
• refactor: Code change that neither fixes a bug nor adds a feature
• perf: Code change that improves performance
• test: Adding missing tests or correcting existing tests
• build: Changes that affect the build system or external dependencies
• ci: Changes to CI configuration files and scripts
• chore: Other changes that don't modify src or test files
• revert: Reverts a previous commit
• BREAKING CHANGE: Introduces a breaking change (can be combined with any type above)

Checklist

• Code follows the style guidelines of this project
• Code has been self-reviewed
• Code has been commented, particularly in hard-to-understand areas
• Code docstring/documentation-blocks for new or existing methods/components have been added or updated
• Unit tests have been added or updated for any new or modified functionality

AI Usage

• None: No AI tools were used in creating this PR
• Light: AI provided minor assistance (formatting, simple suggestions)
• Moderate: AI helped with code generation or debugging specific parts
• Heavy: AI generated most or all of the code changes

[psyke83]

In my opinion, the Flatpak instructions for KMS should be removed from the docs and packaging/linux/dev.lizardbyte.app.Sunshine.metainfo.xml. It's telling users basically to run as root, which seems risky even when you acknowledge it's sandboxed.

Edit: also, to clarify, you cannot install a service vendor preset to any folder in the user's /home that systemd will recognize. That's another reason why the KMS service is not a good idea to install in this case, as both services will default to enabled and thus may conflict in unpredictable ways.

I also investigated the AppImage "install" behaviour: Ubuntu 25.10's default AppArmor policy blocks setuid from being performed in a fusermount3 fs (which is used by AppImage), so there's no point in trying to install a kms service & preset for that case as well, since we can't even set the cap_sys_admin capability needed for the KMS service.

Will I update the PR with these conclusions in mind? I can keep the lines in the AppArmor scripts, but they won't work unless/until a workaround is devised for the AppArmor policy, which may never happen.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Bundle Report

Bundle size has no change ✅

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 15.10%. Comparing base (b63e1af) to head (014c1ae).
⚠️ Report is 1 commits behind head on feat/linux/add-xdg-portal-grab.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                        Coverage Diff                         @@
##           feat/linux/add-xdg-portal-grab    #4626      +/-   ##
==================================================================
+ Coverage                           14.81%   15.10%   +0.28%     
==================================================================
  Files                                  95       95              
  Lines                               20099    19715     -384     
  Branches                             9401     9072     -329     
==================================================================
  Hits                                 2977     2977              
+ Misses                              15985    15049     -936     
- Partials                             1137     1689     +552     

Flag	Coverage Δ
Archlinux	11.09% <ø> (+0.01%)	⬆️
FreeBSD-14.3-amd64	13.24% <ø> (+0.02%)	⬆️
Homebrew-ubuntu-22.04	13.33% <ø> (ø)
Linux-AppImage	11.49% <ø> (+0.01%)	⬆️
Windows-AMD64	13.44% <ø> (+0.07%)	⬆️

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see 36 files with indirect coverage changes