TechTimeRo good to hear!
Unfortunately we have not really defined a recommended table prefix length in Flarum so extensions don't take this into account for their index length.
You just need 2 less characters in your prefix to solve this particular error (max 64 characters length for the index name). But other extensions could have longer index names 😅 If you can avoid using a prefix, it's the safest method. Otherwise I could recommend 3 or 4 characters for the prefix length to be on the safe side.
We should do something to handle the error in a friendlier way, but I'm not sure how to handle this. We could throw a better exception when it happens, but it will still fail mid-migration which isn't great. In this extension we could provide a shorter index base name to try to avoid the issue, but there will still be a max prefix length to watch out for.
