> I have an issue with m'y New HP m209dw. [...] I have just the message that the
> ppd need a cups filter but if i am not wrong we don't need this filter ?

If the printer doesn't speak PostScript, it does need a driver ('cups filter') to translate the native printer language to PostScript. According to the official specs (also quoted there, #23), it speaks PCLmS, URF and PWG, neither of which MorphOS has a driver for.

See there for a list of non-PS printer languages a MorphOS driver currently exists for:
https://morph.zone/modules/newbb_plus/viewtopic.php?topic_id=13689&forum=9&start=9 (#10)