justshipit There is a guarantee you won't lose data, because updates won't be forced. The question is will your current data work with a higher version and whether you corrupt your own database by trying to upgrade ..
At this point in beta design choices are made that require either a very complicated update process or change one line in one of the original files of Flarum core.
1. simple but possibly non-forward compatible change
For instance an issue exists that require one change in a database table creation file or a complex upgrade script. If you've read @Franz response, it's suggested to do the easy fix, because "I think we can just cheat (we're still beta, hey) and fix it in the existing migration". And that's a logical choice, there is no reason to complicate an initial installation with upgrades meant for a non-stable release.
So how does that effect your installation?
Simple, once that change has been added to a new release and your code seems to break, you will have to run those database changes manually. Can you do that? Will you lose data when you do? That's all up to you.
2. complexer forward compatible change
Another example is the addition of this migration, added in December of last year. It changes the column type of "value" in the "settings" table to text instead of blob. Which allows for easier editing of those fields with a database tool.
This is a great example of a change that could have been modified in the initial database migration, but was added seperately to ease upgrading.
what can you do?
- don't use an unstable version; the obvious choice.
- make backups before upgrading, not a suggestion but a requirement (database and files please).
- don't upgrade; I mention this because it's an actual choice, but not a valid one ? because upgrades might patch security issues.
- get help when you get stuck during upgrades you do yourself.
We advice everyone to not use Flarum in production because it's not stable. Whether you like a challenge and are up to get your hands dirty is up to you, we won't force you against using Flarum beta or deny you the freedom to ask questions.