Except Roblox is currently working on providing unofficial support to Wine (and by extension Roblox). See the post from one of their employee: https://devforum.roblox.com/t/why-did-roblox-stop-supporting-linux-users (Need to be logged in)
Oh I forgot to mention that tools like Illustrator and Inkscape are better tools for stuff that needs to be scaled into various sizes (like logos).
If you want a more in depth explanation, Photoshop and Gimp specializes in rasterised images (images made of pixels) whereas Illustrator and Inkscape specializes in vector images (images made of graphs). When you scale up or down a rasterized image, the detail changes along with it because you see bigger or smaller pixels. When you do the same with a vector image, the math stays the same; the quality stays sharp as a result.
Disclaimer: I'm no expert in this field and am only providing this explanation from my personal experience.
I don't think the zip part will be visible at an icon scale. Ig if it helps, you could try to view the icon at like 5% or less while you're making it
I'm surprised Lemmy.zip is only a week old. With the kind of activity I've being seeing, you'd think this was an established instance. Congratulations!