Just wanted to ask the veterans, can you use the solo expansion with the normal missions that come with the core game?
As the BGG description for Conflict of Heroes: Eastern Front – Solo Expansion notes:
Note: The base game 2-player scenarios are NOT playable with solitaire rules "out of the box"; solitaire scenarios need additional elements (mission track etc). So additional homebrew tinkering is needed to adapt an existing 2-player scenario for use with the solitaire system. But the solitaire expansion comes with many (new) scenarios, and the Firefight Generator expansion permits creating solitaire scenarios.