May I ask what your config was, such as distro, packaging format, and extensions were used? Also, what hardware?
Additionally, what issues specifically were you experiencing specifically? Were sites just loading slowly?
I ask because I’ve used recent versions Firefox on decently old hardware with 4 GB of RAM and 2 cores and had almost no problems. Everything rendered correctly and in a reasonable amount of time. I’d be curious to know why that isn’t happening for you.
Most browsers support it, but most web apps, including some Google Suite stuff ironically, don’t support uploading a webp.