I’ve looked further and I have an AMD CPU which seems to be an usual culprit with snaps as linked by @aibd. Seems the snap published uses the snap Core18, and an advice somewhere was to go to Core20. So to avoid this it seems the easy-installer snap would need to be updated.
I finally built it from source, but I also encountered an error already reported on the forum. Maybe the instruction on https://doc.e.foundation/easy-installer-contribute#how-to-build should be updated to use the command JAVA_HOME=buildSrc/linux/jdk-11.0.2 ./gradlew dist.
With the right command, it was trivial to build. But I still hope this appimage merge request [1] can be merged soon 
Now, going to look for a way to backup my phone to restore it after the upgrade, as using easy-installer erases everything.
[1] https://gitlab.e.foundation/e/devices/easy-installer/-/merge_requests/217