[fr0sty]

I'll put in a vote for: https://lcwo.net/ (Learn CW Online)

If your goal is to be "conversational" in CW I suggest you crank up the character speed until you are not able to count individual dits/dahs anymore. This will probably be somewhere in the 25-35WPM range. The goal is "instant character recognition" where you hear the sound/shape of the entire character rather than counting elements, assembling them in your head, and doing a mental hash lookup on the result.

If you have trouble receiving or copying down the 5letter groups at this speed resist the temptation to add "farnsworth" spacing (extra gaps between letters). Instead increase the word spacing until you have enough down time in between to get everything copied.