I use a plugin called Video Speed Controller, it‘s probably my most used browser extension. You can configure hotkeys as well, which makes it very convenient. I use Q/E for -0.5/+0.5 and A/D for -0.1/+0.1 so I can finetune the playback to my liking with just couple keypresses.
There’s also a small window in the top left of the video showing the current speed, which you can toggle by pressing V.