The plan is to release something functional this spring. If all goes well with ESS roll-out, then it may be sooner.
This looks very promising. Any plan to offer the ability to self-host the sync server after ESS will be rolled-out?
This is not in the plans right now, but it will be considered after more urgent features are done. It’s quite niche as you probably understand, so other work takes higher priority.
A niche, well yes and no. One of the main reason to leave a service like Todoist is (probably for many?) that it is expensive. Paying something once is really a great option. If sync implies to pay every month/year, that might be a reason not to make the switch!