Curious how you're handling the isolation/sandboxing model here? The standard Chrome approach of site isolation + process-per-extension becomes pretty heavy on mobile. Have you considered using a shared process model with context isolation instead? We found that careful use of V8 contexts could give similar security guarantees with ~70% less memory overhead, though it required some tricky IPC handling between the extensions and main browser process.
Also worth noting that the WebExtension manifest v3 transition adds some extra complexity for mobile browsers - particularly around the service worker lifecycle and background page limitations. Would love to hear how you're approaching that migration path.
The cool part about Helium is that it's based on patches, rather than forking the full source code. I don't know how sustainable this is in the long term, but it's an interesting approach for sure.
That would raise the value of that project quite a lot (at least for me, but I feel like there are others, thinking similarly).
Please, push it to F-Droid!
Edit: hard to find where to get this browser. Do I need to build it myself?
Have you thought about merging your efforts with ungoogled-chromium (Android)?
There USED to be an ungoogled-chromium for Android (circa v88 chrome, the APK is still available for download) that also allowed extentions.