We decided to go to LTSC for all classrooms and admin PC's.  We knew there be certain staff that would need the store app for business purposes creating an "exception to the rule."

I searched google:

https://github.com/kkkgo/LTSC-Add-MicrosoftStore

The script posted adds 3 components back to windows, one is the store.  Make sure you read the directions, it tells you how to remove components you do not want.

I tweeked that add-store cmd file to add just the .net back to my golden LTSC image

@echo off
for /f "tokens=6 delims=[]. " %%G in ('ver') do if %%G lss 16299 goto :version
%windir%\system32\reg.exe query "HKU\S-1-5-19" 1>nul 2>nul || goto :uac
setlocal enableextensions
if /i "%PROCESSOR_ARCHITECTURE%" equ "AMD64" (set "arch=x64") else (set "arch=x86")
cd /d "%~dp0"

for /f %%i in ('dir /b *WindowsStore*.appxbundle 2^>nul') do set "Store=%%i"
for /f %%i in ('dir /b *NET.Native.Framework*1.6*.appx 2^>nul ^| find /i "x64"') do set "Framework6X64=%%i"
for /f %%i in ('dir /b *NET.Native.Framework*1.6*.appx 2^>nul ^| find /i "x86"') do set "Framework6X86=%%i"
for /f %%i in ('dir /b *NET.Native.Runtime*1.6*.appx 2^>nul ^| find /i "x64"') do set "Runtime6X64=%%i"
for /f %%i in ('dir /b *NET.Native.Runtime*1.6*.appx 2^>nul ^| find /i "x86"') do set "Runtime6X86=%%i"
for /f %%i in ('dir /b *VCLibs*140*.appx 2^>nul ^| find /i "x64"') do set "VCLibsX64=%%i"
for /f %%i in ('dir /b *VCLibs*140*.appx 2^>nul ^| find /i "x86"') do set "VCLibsX86=%%i"

if /i %arch%==x64 (
set "DepStore=%VCLibsX64%,%VCLibsX86%,%Framework6X64%,%Framework6X86%,%Runtime6X64%,%Runtime6X86%"

set "PScommand=PowerShell -NoLogo -NoProfile -NonInteractive -InputFormat None -ExecutionPolicy Bypass"

1>nul 2>nul %PScommand% Add-AppxProvisionedPackage -Online -PackagePath %Store% -DependencyPackagePath %DepStore% -LicensePath Microsoft.WindowsStore_8wekyb3d8bbwe.xml
for %%i in (%DepStore%) do (
%PScommand% Add-AppxPackage -Path %%i
)
%PScommand% Add-AppxPackage -Path %Store%

You can create a SMA script to add the store for existing LTSC deployments.