Created attachment 102370 [details] emboss effect, before and after Version 3.0.93.0 to be exact, though the previous 3.1 beta I tried did the same thing. Emboss is broken, at least for me. I have a pretty standard setup, Win10, Cintiq, drivers all up to date. Embossing, whether it's via filter or adjustment layer, turns the canvas gray and the emboss effect looks like interlaced pixels around the edge. I've attached a before and after screenshot.
Well... Krita's emboss filter comes from GIMP, not Photoshop and works like Gimp' s filter: https://docs.gimp.org/nl/plug-in-emboss.html -- not that it doesn't need improvements, but given that the filter is now 13 years old and nobody has stepped up to work on it, chances are slim for that to happen.
Correction, the filter comes from Digikam, though I guess they were inspired by Gimp.