Can't get QLMarkdown to work in Monterey

I'm trying to do what should be a fairly simple task: have Finder and Quick Look view .md and .markdown files as if they had the extension .txt. As per previous answers on this topic, I had installed the QLMarkdown plugin in my /Library/Quicklook to make this happen, and it was working fine for a while. Recently I had a hardware disaster that required Apple to wipe and replace my hard drive, with the new one running Monterey. In this new system, the QLMarkdown plugin is not working. I tried copying the latest version (1.3.6) into the /Library/Quicklook and, as per the readme , I ran qlmanage -r in the terminal to refresh. Then I got an error from Apple saying it would not run because Apple could not check it for malicious software. No option to override. The previous answers suggest I could install Homebrew and run "brew cask install qlmarkdown", but following the [Homebrew install instructions](https://brew.sh/) wound up causing a system freeze and reboot - and QuickLook wasn't working any better after that. How do I get QuickLook to recognize Markdown on Monterey under these circumstances?