Skyrim Special Edition on Xbox Game Pass allows this but comes with one important caveat: the Skyrim Script Extender (SKSE) is incompatible with this version.
However, some games on the Xbox Game Pass app allow for an optional toggle button that can allow mod installs by opening up the root game folder including the game’s executable. When a game is purchased either through the Microsoft Store or Xbox Game Pass for PC, the files are installed into read-only directories which makes them impossible to access and therefore unable to be modded. However, one concern that was raised included mod support, and it seems like Skyrim Special Edition does include full support for mods, but is actually severely limited by one important factor.
Last week Microsoft finalized their massive $7.5 billion acquisition of Zenimax Media - the parent company of many big game studios including Bethesda - which meant many more Bethesda games had become available on Xbox Game Pass.