I think it's fair to say you should not use anything to browse the web but something like lynx.

Firefox is not good enough, see https://digdeeper.neocities.org/articles/mozilla

Some browsers:
https://surf.suckless.org/ C, webkit gtk, the suckless web browser

• tab support with suckless tabbed:wa

https://github.com/jun7/wyeb C, webkit gtk, vim-like browser
https://qutebrowser.org/ Python, qt webengine

• adblocking via python-adblock
• WebGL works
• native global dark mode
• KeePassXC extension
• keep bookmarks via html file converted from markdown

Block content with a light, opensource and updated ad blocker like uBlock Origin.

Recommend adding https://oisd.nl/ lists to uBlock where possible.
Use a good DNS resolver or host your own.

You can save web pages as a single HTML file with SingleFile. It saves the page as-is with images and everything.

• Disable pocket with extensions.pocket.enabled = false

You can save write operations by disabling/moving cache and profile to RAM, and syncing the profile directory to disk.

See Firefox/Profile on RAM for more info.

Setup profile-sync-daemon, see the arch wiki for more info.

You can disable disk cache with browser.cache.disk.enable = false
Alternatively, you can move it into RAM with a tmpfs directory: set browser.cache.disk.parent_directory = /run/user/UID/firefox, where UID is your user's ID (usually 1000, check: id -u)