I'll be shocked if it's functional within 3 years.

Thanks I seem to have missed that mention, however, I don't think it implies a linux client is actually in development.

The October Update says they are improving the SDK in anticipation of the Linux app, much like your July one says.

It would be interesting to know a more concrete date, even if only what quarter they are targeting (or hell, I'd settle for whether they expect it to release next year or not).

It’s possible that they’ve improved it in that time. At least my experience hasn’t been bad but I was doing a once off migration, not continual syncs.

Their Proton Drive integration is still in beta though.

I use Proton Drive with a mounted rclone folder and it's gotten better, but it is still not as smooth as the sync on my Windows machine unfortunately.

I kind of understand it though. Their official client is gtk based, there are distros that use qt, other distros don't use anything at all and instead the user build it. I ended up using wireguard/openvpn directly and just downloading proton config files and it worked greatly.

If they just provide a good server infrastructure and a reasonable app that works well on famous distros e.g Ubuntu, Fedora, it's enough