You can do your own sync in a hacky manner - but if I were going down that route, I'd just choose one of the more open (and cheaper) alternative devices.
A friend of mine uses an Onyxbook (not sure what model) extensively for note taking and he seems pretty happy with it. Software developer with a bit of math thrown in, to get an idea of what he writes on it.
I'm being a bit future-looking here and considering alternatives to the gen3 reMarkable, not the current hardware. Specifically, the PineNote seems like it could fill the niche for me.
I have a BOOX Max Lumi, it has all those features, for free. Plus is a fully functioning android tablet.
I'm in the market for alternatives. What equivalent devices are both cheaper and more open? I haven't found any. :(
I got a Supernote and its a bit cheaper and has really great features. Remarkable shies away from anything but writing, so sync is limited - while the supernote has great calendar sync thats come in handle for note taking.
The Onyx Boox series come in different sizes and are just Android with a custom launcher, and they're cheaper and with more choice (most notably regarding screen size).
Caution however, the company violates the GPL, which might be a deal-breaker for some.