The SM124 is compatible with essentially all Atari ST - after all, the clean B&W video mode was one of the main selling points for the ST series - at least in Europe, were it had a strong stand as professional machine.
The STE series does not differ from previous models in terms of video signal generated. All STE enhancements in video are in generation:
- 4096 instead of 512 colours to choose from (CLUT)
- ability for external synchronisation (genlock)
- horizontal and vertical scrolling (screen addressing)
- Blitter add-on
While the signal generated is still within the same specs:
- 640x400 max resolution
- 70 Hz max
- (16 colours at a time)
It wasn't until the Falcon 030 (and TT030) that new modes were available - its video generator was quite programmable - although, still compatible with existing screens including the SM124.
There's a real nice Video about ST-Video (French language). It goes into great detail about modes and displays, including differences between European and US. Connectors, cables and similar are described as well. Most of the examples seem to be made using a 1040.