There is a legacy version of PolyMC, primarily for older versions of Windows like Windows 7 or Windows 8.1.
You can download it here:
Advanced Windows install options
winget install -e PolyMC.PolyMC
scoop bucket add games scoop install polymc scoop install polymc-qt5 #if you want Windows-Legacy instead
choco install polymc
Chocolatey and Scoop packages are community-maintained, PolyMC is not responsible for outdated versions.
A community maintained portable installer for PolyMC can be found here.