$env:SHELL only works when Powershell is set to default

[thebitstick]

powershell-wtf/WTF.psm1

Line 173 in ea6ebcb

/usr/bin/env sudo $env:SHELL -nologo -Command "& $args"

Using $env:SHELL only works on systems that have their shell set as Powershell.
How about first checking if the current is pwsh, if not, then check if pwsh-preview exists, if not, then default to pwsh.