Server config: Windows, xampp, PHP 7.1.8, MySQL 5.6.16
After a fresh install I got an error while I try the search. (Oops! Something went wrong. Please reload the page and try again.)
After hard refresh the page or loading the url direct, I got this error with and without debug mode on:

While this error is shown the page switching no longer working correct: (after click "profile settings")

I found this error in the flarum logfile:
Next Illuminate\Database\QueryException: **SQLSTATE[42S22]: Column not found: 1054 Unknown column** 'f123456789posts_ft.most_relevant_post_id' in 'field list' (SQL: select `f123456789discussions`.*, `f123456789posts_ft`.`most_relevant_post_id` from `f123456789discussions` inner join (select `f123456789posts`.`discussion_id`, SUM(MATCH(`f123456789posts`.`content`) AGAINST (123456)) as score, SUBSTRING_INDEX(GROUP_CONCAT(`f123456789posts`.`id` ORDER BY MATCH(`f123456789posts`.`content`) AGAINST (123456) DESC, `f123456789posts`.`number`), ',', 1) as most_relevant_post_id from `f123456789posts` where exists (select 1 from `f123456789discussions` where `f123456789discussions`.`id` = `f123456789posts`.`discussion_id` and not exists (select 1 from `f123456789discussion_tag` where 0 = 1 and `f123456789discussions`.`id` = `discussion_id`) and (`f123456789discussions`.`is_private` = 0 or (`f123456789discussions`.`is_approved` = 0))) and (`f123456789posts`.`is_private` = 0 or (`f123456789posts`.`is_approved` = 0)) and `f123456789posts`.`type` = comment and MATCH(`f123456789posts`.`content`) AGAINST (123456 IN BOOLEAN MODE) and `type` in (comment, discussionRenamed, discussionLocked, discussionStickied, discussionTagged) group by `f123456789posts`.`discussion_id`) `posts_ft` on `f123456789posts_ft`.`discussion_id` = `f123456789discussions`.`id` where not exists (select 1 from `f123456789discussion_tag` where 0 = 1 and `f123456789discussions`.`id` = `discussion_id`) and (`f123456789discussions`.`is_private` = 0 or (`f123456789discussions`.`is_approved` = 0)) and (MATCH(`f123456789discussions`.`title`) AGAINST (123456 IN BOOLEAN MODE) or `f123456789posts_ft`.`score` is not null) and not exists (select 1 from `f123456789discussion_tag` where 0 = 1 and `f123456789discussions`.`id` = `discussion_id`) order by MATCH(`f123456789discussions`.`title`) AGAINST (123456) desc, `f123456789posts_ft`.`score` desc limit 21) in C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Connection.php:664
Stack trace:
#0 C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Connection.php(624): Illuminate\Database\Connection->runQueryCallback('select `f123456...', Array, Object(Closure))
#1 C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Connection.php(333): Illuminate\Database\Connection->run('select `f123456...', Array, Object(Closure))
#2 C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Query\Builder.php(1719): Illuminate\Database\Connection->select('select `f123456...', Array, true)
#3 C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Query\Builder.php(1704): Illuminate\Database\Query\Builder->runSelect()
#4 C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Eloquent\Builder.php(481): Illuminate\Database\Query\Builder->get(Array)
#5 C:\xampp\htdocs\flarum0.8\vendor\illuminate\database\Eloquent\Builder.php(465): Illuminate\Database\Eloquent\Builder->getModels(Array)
#6 C:\xampp\htdocs\flarum0.8\vendor\flarum\core\src\Discussion\Search\DiscussionSearcher.php(81): Illuminate\Database\Eloquent\Builder->get()
#7 C:\xampp\htdocs\flarum0.8\vendor\flarum\core\src\Api\Controller\ListDiscussionsController.php(87): Flarum\Discussion\Search\DiscussionSearcher->search(Object(Flarum\Search\SearchCriteria), 20, 0)
#8 C:\xampp\htdocs\flarum0.8\vendor\flarum\core\src\Api\Controller\AbstractSerializeController.php(98): Flarum\Api\Controller\ListDiscussionsController->data(Object(Zend\Diactoros\ServerRequest), Object(Tobscure\JsonApi\Document))
#9 C:\xampp\htdocs\flarum0.8\vendor\flarum\core\src\Http\RouteHandlerFactory.php(40): Flarum\Api\Controller\AbstractSerializeController->handle(Object(Zend\Diactoros\ServerRequest))
#10 C:\xampp\htdocs\flarum0.8\vendor\flarum\core\src\Http\Middleware\DispatchRoute.php(67): Flarum\Http\RouteHandlerFactory->Flarum\Http\{closure}(Object(Zend\Diactoros\ServerRequest), Array)
...
And the installer message for prefix is too long not working.
Probably a issue with db prefix?
p.s. You devs should avoid adding the prefix to db indexes/keys.