The doom2.wad is different than the ones from the CD V1.666 and floppy v1.9 releases:
; 14612688 19:53.20 1995-12-02 WinDOOM2.WAD
; 14943400 15:00.00 1994-08-30 DOOM2v1666.WAD
; 14604584 19:55.02 2019-09-28 DOOM2v19.WAD
d7a07e5d3f4625074312bc299d7ed33f *WinDOOM2.WAD
30e3c2d0350b67bfbf47271970b74b2f *DOOM2v1666.WAD
25e1459ca71d321525f84628f45ca8cd *DOOM2v19.WAD
I tried running serdoom.exe with the doomser.dll from the April 13 version, and got this nice error message:
Some files are missing from my copy of the game, wdser32.dll used by the serial game launcher, and help files that may or may not exist for both the serial and network games launchers.