I can personally vouch that Roblox Studio Mod Manager isn’t malicious or dangerous or anything like that. It’s made by @Maximum_ADHD who is well known in the community, and RSMM is open sourced.
It’s been repeatedly flagged by Windows Defender and other AVs for the past year at least, and I reported an issue on it on the repo a while back. I have personally submitted it to Microsoft a few times as safe myself and it was verified by them a couple times, but, each new version is basically a whole different executable to AVs unfortunately.
The executable is unsigned, so every new version AVs identify as a whole different program. It unfortunately can’t really be identified by them because of that. If you took an existing version of RSMM that AVs consider safe, and modified it yourself in a malicious way, it would look no different than a new version of RSMM, since there’s no signing to say “this is an official build”. AVs just can’t identify that it’s actually and official version of RSMM or even that it’s RSMM at all.
If I recall correctly, the reason AVs seem to hate it in the first place is because it downloads another program (Roblox). Commonly trojans will download other malicious programs (and if you think about it even though it comes from roblox.com it doesn’t need to be a safe program, it could even be a safe program that gets exploited, or roblox.com could unknowingly be serving a malicious file from the perspective of an AV).
Roblox itself doesn’t run into this issue because their installer is actually signed and has a verified publisher with it.
The way that RSMM actually works is very unintrusive. It’s pretty much just a Roblox installer, but it adds an extra ClientSettings folder (for fast flags since Roblox will happily load fast flags from there, even the Roblox player will). It will add any plugins or icons or whatever you add to it yourself after installing Roblox. It doesn’t do anything like attach to studio or anything, it just uses official Roblox features to do what it does.
Not telling you to go around trusting random programs or anything, but, I did just wanna provide a detailed explanation about that, since I find it interesting and do want to defend RSMM.
Anyways, I actually came here because Roblox seems to be ignoring ClassImages.png and was hoping someone else would’ve had a solution here but that doesn’t seem to be the case. 
P.s. I want to install it manually since I’m on Linux run Roblox under Wine through Grapejuice, and RSMM is just kind of inconvenient to run in Grapejuice.
