.gitignore I use in my iOS/Mac apps (in each repository, not global)

.gitignore

*~
.DS_Store

####################################################################################################
#
# The following are taken from https://github.com/github/gitignore/blob/main/Global/macOS.gitignore on 28 Mar 2022 (2bb963b dated 6 Jul 2017)
#

# General
.DS_Store
.AppleDouble
.LSOverride

# Icon must end with two \r
Icon


# Thumbnails
._*

# Files that might appear in the root of a volume
.DocumentRevisions-V100
.fseventsd
.Spotlight-V100
.TemporaryItems
.Trashes
.VolumeIcon.icns
.com.apple.timemachine.donotpresent

# Directories potentially created on remote AFP share
.AppleDB
.AppleDesktop
Network Trash Folder
Temporary Items
.apdisk

#
####################################################################################################


####################################################################################################
#
# The following are taken from https://github.com/github/gitignore/blob/master/Swift.gitignore on 28 Mar 2022 (e00d43a dated 7 Aug 2019)
#

# Xcode
#
# gitignore contributors: remember to update Global/Xcode.gitignore, Objective-C.gitignore & Swift.gitignore

## User settings
xcuserdata/

## compatibility with Xcode 8 and earlier (ignoring not required starting Xcode 9)
*.xcscmblueprint
*.xccheckout

## compatibility with Xcode 3 and earlier (ignoring not required starting Xcode 4)
build/
DerivedData/
*.moved-aside
*.pbxuser
!default.pbxuser
*.mode1v3
!default.mode1v3
*.mode2v3
!default.mode2v3
*.perspectivev3
!default.perspectivev3

## Obj-C/Swift specific
*.hmap

## App packaging
*.ipa
*.dSYM.zip
*.dSYM

## Playgrounds
timeline.xctimeline
playground.xcworkspace

# Swift Package Manager
#
# Add this line if you want to avoid checking in source code from Swift Package Manager dependencies.
# Packages/
# Package.pins
# Package.resolved
# *.xcodeproj
#
# Xcode automatically generates this directory with a .xcworkspacedata file and xcuserdata
# hence it is not needed unless you have added a package configuration file to your project
# .swiftpm

.build/

# CocoaPods
#
# We recommend against adding the Pods directory to your .gitignore. However
# you should judge for yourself, the pros and cons are mentioned at:
# https://guides.cocoapods.org/using/using-cocoapods.html#should-i-check-the-pods-directory-into-source-control
#
# Pods/
#
# Add this line if you want to avoid checking in source code from the Xcode workspace
# *.xcworkspace

# Carthage
#
# Add this line if you want to avoid checking in source code from Carthage dependencies.
# Carthage/Checkouts

Carthage/Build/

# Accio dependency management
Dependencies/
.accio/

# fastlane
#
# It is recommended to not store the screenshots in the git repo.
# Instead, use fastlane to re-generate the screenshots whenever they are needed.
# For more information about the recommended setup visit:
# https://docs.fastlane.tools/best-practices/source-control/#source-control

fastlane/report.xml
fastlane/Preview.html
fastlane/screenshots/**/*.png
fastlane/test_output

# Code Injection
#
# After new code Injection tools there's a generated folder /iOSInjectionProject
# https://github.com/johnno1962/injectionforxcode

iOSInjectionProject/

#
####################################################################################################

I think the “Icon” line is what causes custom icons added to files to be ignored. The comment suggests it is important that there are two \r carriage returns after the name which might have been lost when I pasted the contents of my file into this gist. Going to the link in my comment and copying the file and/or line manually should be a way of getting the correct magic characters.