https://www.waterfoxproject.org/blog/waterfox-56.0-release-download

What’s new in Waterfox 56.0.2?

・ e10s will now be disabled when using add-ons that aren’t marked explicitly as compatible with e10s.
　・ If you’d like to force enable e10s, you can by setting browser.tabs.remote.force-enable to true in about:config.
　　Warning: This may cause the add-on or the browser to behave unexpectedly.

ということなので自己責任でe10sを強制的に有効で試せばOK