Fast on Linux and Windows, and supports 3-way merging! Diffinity and Meld are a couple of other viable options.
winget install KDE.KDiff3
@'
[KDiff3 Options]
ApplicationFont=Segoe UI,9,-1,5,50,0,0,0,0,0
CreateBakFiles=false
EncodingForA=UTF-8
EncodingForB=UTF-8
EncodingForC=UTF-8
EncodingForOutput=UTF-8
EncodingForPP=UTF-8
EscapeKeyQuits=true
Font=Cascadia Code,10,-1,5,50,0,0,0,0,0
ReplaceTabs=true
ShowLineNumbers=true
ShowWhiteSpace=true
ShowWhiteSpaceCharacters=false
SkipDirStatus=true
TabSize=4
UnfoldSubdirs=true
'@ | Out-File -Encoding ascii "$env:LocalAppData/kdiff3rc"
git config --global --edit
[diff]
tool = kdiff3
[difftool]
keepBackup = false
prompt = false
trustExitCode = false
[difftool "kdiff3"]
path = C:/Users/jeffmill/AppData/Local/KDiff3/bin/kdiff3.exe
[merge]
tool = kdiff3
[mergetool]
keepBackup = false
prompt = false
trustExitCode = false
[mergetool "kdiff3"]
path = C:/Users/jeffmill/AppData/Local/KDiff3/bin/kdiff3.exe