Since you're looking at print for reference, it is usually very difficult to get the same imperfections with our nice, optimized-for-clarity digital tools. You already have a nice base layer, which with some similar post-processing can get you what you want. I find it helpful to look at the reference you have in mind and then work backwards from it layer by layer. For example, you can zoom into risograph prints to look at the textures or look at how people recreate print misregistration/ink offset in Photoshop to start with and then try to translate it into code (or just Photoshop if you like!). I gave it a quick shot but more can be done: https://i.ibb.co/QvZvjNpf/output.png

magick input.png \ \( +clone -blur 0x0.6 -roll +1+1 -level 60%,100% \) -compose Darken -composite \ -level 48%,55% \ \( +clone +level-colors grey50 -attenuate 3.5 +noise Gaussian -colorspace gray \ -alpha set -channel A -evaluate set 10% +channel \) \ -compose Hardlight -composite \ output.png