This Website: https://earth.nullschool.net/ is Working way better (not perfect) in “Samsung Galaxy S2” (Lineage) with Fenec Webbrowser but not in Fairphone 2 (FP-Open) with Firefox, have to wait for a long time after every fingertip.
Works well in my FP2 (Lineage 14.1, Firefox) and Nexus 4 (Lineage 15.1, Fennec). I guess performance is similar to the “not perfect” you stated above.
I got way better results (perfect) with Firefox Focus/Klar, which uses the Blink engine embedded in your system, instead of a shipped Gecko like Firefox/Fennec. Probably the developer didn’t have in mind Gecko engines to begin with (bad practice which drives us to bad monocultures…)