Chromium-based browsers have arguably better security than Firefox. https://madaidans-insecurities.github.io/firefox-chromium.html
Vanadium further improves Chromium's security by disabling the JS JIT Compiler, using a hardened memory allocator (GrapheneOS hardened_malloc) enabling ARMv8.5 MTE, and applying other hardening patches (https://github.com/GrapheneOS/Vanadium/tree/main/patches).
The secureblue project maintains a hardened Chromium build for Linux called Trivalent, which uses most of the patches from Vanadium, among others. You can get it from their repo: https://repo.secureblue.dev/secureblue.repo
You could add secureblue. I would put it in the same category as GrapheneOS and Vanadium.