For the last couple of months, I have been using a set up in which I have copies of a single file TiddlyWiki for notes on my desktop, tablet and phone, and the three copies of the same wiki synchronize with each other on a tiddler level.
The sync is via an in-development plugin (Harmony) that synchronizes tiddlers to a private GitHub repo which essentially serves as a free sync server, with the user not requiring any knowledge of git. Any changes to a wiki configured to sync to a given repo are automatically propagated to other wikis syncing to the same repo.
Essentially this is the same model used by apps such as Evernote, where you have different instances of the app on different devices that can all work separately and offline, but they also sync with each other via a server. Here, the private GitHub repo plays the role of a no configuration necessary free server, and you retain full control over your data. Creating a private GitHub repo is very easy even for non-technical users, whereas setting up your own server securely can be a complex undertaking.
This setup allows for use cases like synchronizing a wiki between devices at the tiddler level; ensuring that changes in one tab aren’t overwritten by an instance of the same wiki open in another tab or device; or being offline for an extended period and syncing any changes made to other devices once online.
The driver for this design choice is that I need offline access to my wikis at all times, so online hosting solutions are a non-starter for me. Were online hosting an option, I would likely choose TiddlyPWA.
Currently the plugin works robustly enough that I have been using it on a daily basis since February. It would need a rewrite to make it usable for a wider audience, which I will admit that I am currently struggling to find motivation for given that it already works very well for my very specific use cases, and I am not sure that many others would find this useful.
PS: a useful though unplanned benefit of this approach is that you get a per tiddler history of changes in the GitHub repo and it would theoretically be possible to revert a wiki back to a specific time in the history of changes.