I have been building zero install security tools where the browser is the base. I wrote about the “why” here https://blog.anantshri.info/making-security-tools-accessible-why-i-chose-the-browser/
I realized many others are building similar browser-first tools, so I made a curated collection: https://anantshri.github.io/awesome-in-browser-security-tools/
RT, PRs & links welcome