selenium_cdp VS i2p.plugins.firefox

https://github.com/sergueik/selenium_cdp is in Java but does what you're asking and has many examples of the other API calls.

I use Firefox with the I2P In Private Browsing webextension for mixing I2P and clearnet browsing in the same browser, and I use i2p.plugins.firefox for I2P-only browsing.

The only package that directly incorporates an I2P-specific browser profile is the Easy-Install for Windows. To get an I2P-focused profile manager as a Debian package, you can use https://github.com/eyedeekay/i2p.plugins.firefox/releases/download/1.0.9/i2pbrowser_1.0.9_amd64.deb. This is exactly the same profile manager code as the Easy-Install bundle, but it is decoupled from the I2P router itself. To make the router launch it for you, add routerconsole.browser=/opt/i2pbrowser/bin/i2pbrowser to your router.config file.

If you want the benefits of the Easy-Install on your existing Classic install, your best option is to use a console plugin IMO. You can download: https://github.com/eyedeekay/i2p.plugins.firefox/releases/download/1.0.8/i2pfirefox.su3 and install it using the interface on: http://localhost:7657/configplugins after installing there's a period where profiles are unpacked, configs are updated, and the proxy is checked after which you'll see a Firefox browser window open which is configured to use I2P, and a second menu in your System Tray which you can use to manage browsing sessions.

There's also a freestanding I2P Firefox profile manager that does the same thing without managing your I2P session and does not require the easy-install, https://github.com/eyedeekay/i2p.plugins.firefox.

The hard way is to create a browser.config file which can be read by the Easy-Install bundle. This file contains a list of browser names and paths to search for those names in. An example browser.config file can be found at my github: https://github.com/eyedeekay/i2p.plugins.firefox/blob/main/browser.config, by removing all irrelevant(non-Firefox, non-Windows entries) you may configure your Easy-Install bundle to use Firefox instead.

wget https://github.com/eyedeekay/i2p.plugins.firefox/releases/download/1.0.8/i2pbrowser.tar.gz

You can either use an entirely separate browser profile, like with the Easy-Install Bundle for Windows and i2p.plugins.firefox, or you can use a container tab under your main Firefox session.

Of these, Tor Browser requires the least modification, but Firefoxes can be made into a state where they are suitable for most browsing and some otherwise important purposes. That is why I favor using a profile manager which prioritizes Tor Browser and Firefox variant compatibility like https://github.com/eyedeekay/i2p.plugins.firefox

This is browser storage, and has nothing to do with I2P. I can't help you if you're using a misconfigured browser. If you are concerned about managing browser storage, I have half a dozen applications which can help you do this in a modern, portable, routine and secure way. I suggest using this one. Alternatively, This one. If you insist on doing it yourself, enjoy all the reading.

The releases of i2p.plugins.firefox are available on Github for now.