I've yet to read about any pre-2B5 board that works reliably (i.e. also tested successfully with Linux, because that works harder on the memory than MorphOS) with 2× 1 GiB, and even with 2B5 it's hit or miss. Theoretically
, all boards from 2B1 on should work with 2× 1 GiB, because that's what the official mainboard specs
here is succesfull 2GB with rev 2B1 2GB on Pegasos 2 rev 2B1
And as I gave him some advices when he installed and tested MintPPC it looks that it works with linux.
But this is the only Pegasos 2B1 revision with 2GB I know about.
AmigaOS3: Amiga 1200
AmigaOS4: Micro A1-C, AmigaOne XE, Pegasos II, Sam440ep, Sam440ep-flex, AmigaOneX1000
MorphOS: Efika 5200b, Pegasos I, Pegasos II, Powerbook G4, Mac Mini, iMac G5, Powermac G5 Quad