Depending on how far you want to go, there are VNC clients[1], toltec has opkg-installable stuff including at least one browser[2] known to work, and there are full OS replacements that let you run a full linux GUI[3] which can almost certainly run a normal-ish desktop browser.

So while this one won't work, there are options.

[1] https://github.com/reHackable/awesome-reMarkable [2] https://toltec-dev.org/ [3] http://www.davisr.me/projects/parabola-rm/

Any Android-based device.

Potentially in future, Linux-based devices which can run Android apps.

I'm not a particular fan of Android. Its application ecosystem is a bonus though.

Again, this is installable through F-Droid.