> I too have upgraded my card to a Radeon RX550 and quite happy with
> how it works with OS4. [...] If you really want to try out MorphOS on this
> motherboard you need a Radeon X1650-1950 card [...]. On the X5000
> with a X1650-1950 card [...] You won’t have any legacy Warp3D software

Let's not forget that legacy Warp3D support gets lost on OS4 with jumping from a GCN1-based card to a GCN4-based card like your RX550 also.

> 3D support is patchy

What does that mean?

> the further up you go the card tree the worse the support and
> less things will run.

True, and the MorphOS hardware compatibility page clearly states which cards are supported in 2D+3D, 2D+overlay or just 2D.

> Linux performance suffers too with anything less than a series 6000 card

The author of comment #14 pointed out that Linux is good enough with anything from R600 (= HD2000 series) up and that Evergreen cards (= HD5000 series) are among the best supported. Maybe this is different between x64 Linux and PPC Linux?

> They [...] said they have no interest in supporting newer graphics cards

Is this what they really said or just what you think they said? I guess it's more about the available developer resources than about interest per se.