Currently the RX 5700 XT support is undergoing lots of debugging.
If anyone would like to know the status of RX 5700 support I would keep an eye on this:
The most recent complaints on that thread seem to be improving where people are seeing sdma hangs less often.
I would like to think we will have full support by Linux 5.4, but it might be Linux 5.5 if this keeps moving at this pace.
Obviously the Solus Devs never give an ETA on this stuff so I would just watch that link for now for those who really want to know how development outside of Solus is going.
As a side note I did swap out my RX 580 with the RX 5700 XT and only got a black screen on Linux 5.3 for those who might want to try.