I’m a big free software advocate, but unfortunately I don’t think LibreJS fits as a Privacy Guides recommendation. I’m definitely in the camp that software will always be more trustworthy if it’s FOSS, but the GNU Project/FSF does overstate the misconception that free software is always inherently (more) secure or that proprietary software is always inherently totally unsafe for anyone to use in any scenario. Another downside is that it’s exclusively for Firefox, which itself may be considered for removal from Privacy Guides.
I’d say NoScript would be a better option for what you’re suggesting as it can block all scripts and is available for both Firefox and Chromium, however all current recommendations allow the user to block scripts with uBlock Origin, NoScript, or Brave Shields depending on the browser they chose.