This extension does not have the SEO extension set as dependency, although it seems that it requires it to function (the blog page says "An error occurred [...]" and the following is logged):
flarum.ERROR: Exception: V17Development\FlarumSeo\Extend::setTitle(..): Container was not yet initialized. in /app/vendor/v17development/flarum-seo/src/Extend.php:196
Stack trace:
#0 /app/vendor/v17development/flarum-seo/src/Extend.php(36): V17Development\FlarumSeo\Extend::throwError()
#1 /app/vendor/v17development/flarum-blog/src/Controller/BlogOverviewController.php(40): V17Development\FlarumSeo\Extend::setTitle()
#2 /app/vendor/flarum/core/src/Frontend/Frontend.php(62): V17Development\FlarumBlog\Controller\BlogOverviewController->__invoke()
#3 /app/vendor/flarum/core/src/Frontend/Frontend.php(54): Flarum\Frontend\Frontend->populate()
#4 /app/vendor/flarum/core/src/Frontend/Controller.php(32): Flarum\Frontend\Frontend->document()
#5 /app/vendor/flarum/core/src/Http/RouteHandlerFactory.php(41): Flarum\Frontend\Controller->handle()
#6 /app/vendor/flarum/core/src/Http/Middleware/ExecuteRoute.php(27): Flarum\Http\RouteHandlerFactory->Flarum\Http\{closure}()
#7 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ExecuteRoute->process()
#8 /app/vendor/malago/flarum-achievements/src/Middlewares/MiddlewarePosted.php(27): Laminas\Stratigility\Next->handle()
#9 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Malago\Achievements\Middlewares\MiddlewarePosted->process()
#10 /app/vendor/flarum/core/src/Http/Middleware/ContentTypeOptionsHeader.php(21): Laminas\Stratigility\Next->handle()
#11 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ContentTypeOptionsHeader->process()
#12 /app/vendor/flarum/core/src/Http/Middleware/ReferrerPolicyHeader.php(30): Laminas\Stratigility\Next->handle()
#13 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ReferrerPolicyHeader->process()
#14 /app/vendor/flarum/core/src/Http/Middleware/FlarumPromotionHeader.php(30): Laminas\Stratigility\Next->handle()
#15 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\FlarumPromotionHeader->process()
#16 /app/vendor/flarum/core/src/Http/Middleware/ShareErrorsFromSession.php(57): Laminas\Stratigility\Next->handle()
#17 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ShareErrorsFromSession->process()
#18 /app/vendor/flarum/core/src/Http/Middleware/CheckCsrfToken.php(36): Laminas\Stratigility\Next->handle()
#19 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\CheckCsrfToken->process()
#20 /app/vendor/flarum/core/src/Http/Middleware/ResolveRoute.php(67): Laminas\Stratigility\Next->handle()
#21 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ResolveRoute->process()
#22 /app/vendor/flarum/core/src/Http/Middleware/SetLocale.php(51): Laminas\Stratigility\Next->handle()
#23 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\SetLocale->process()
#24 /app/vendor/flarum/core/src/Http/Middleware/AuthenticateWithSession.php(31): Laminas\Stratigility\Next->handle()
#25 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\AuthenticateWithSession->process()
#26 /app/vendor/flarum/core/src/Http/Middleware/RememberFromCookie.php(52): Laminas\Stratigility\Next->handle()
#27 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\RememberFromCookie->process()
#28 /app/vendor/flarum/core/src/Http/Middleware/StartSession.php(61): Laminas\Stratigility\Next->handle()
#29 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\StartSession->process()
#30 /app/vendor/flarum/core/src/Http/Middleware/CollectGarbage.php(46): Laminas\Stratigility\Next->handle()
#31 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\CollectGarbage->process()
#32 /app/vendor/flarum/core/src/Http/Middleware/ParseJsonBody.php(28): Laminas\Stratigility\Next->handle()
#33 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ParseJsonBody->process()
#34 /app/vendor/migratetoflarum/canonical/src/Middlewares/CanonicalRedirectMiddleware.php(49): Laminas\Stratigility\Next->handle()
#35 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): MigrateToFlarum\Canonical\Middlewares\CanonicalRedirectMiddleware->process()
#36 /app/vendor/flarum/core/src/Http/Middleware/HandleErrors.php(57): Laminas\Stratigility\Next->handle()
#37 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\HandleErrors->process()
#38 /app/vendor/flarum/core/src/Http/Middleware/InjectActorReference.php(25): Laminas\Stratigility\Next->handle()
#39 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\InjectActorReference->process()
#40 /app/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(76): Laminas\Stratigility\Next->handle()
#41 /app/vendor/middlewares/request-handler/src/RequestHandler.php(84): Laminas\Stratigility\MiddlewarePipe->process()
#42 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Middlewares\RequestHandler->process()
#43 /app/vendor/middlewares/base-path-router/src/BasePathRouter.php(101): Laminas\Stratigility\Next->handle()
#44 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Middlewares\BasePathRouter->process()
#45 /app/vendor/laminas/laminas-stratigility/src/Middleware/OriginalMessages.php(36): Laminas\Stratigility\Next->handle()
#46 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Laminas\Stratigility\Middleware\OriginalMessages->process()
#47 /app/vendor/middlewares/base-path/src/BasePath.php(73): Laminas\Stratigility\Next->handle()
#48 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Middlewares\BasePath->process()
#49 /app/vendor/flarum/core/src/Http/Middleware/ProcessIp.php(24): Laminas\Stratigility\Next->handle()
#50 /app/vendor/laminas/laminas-stratigility/src/Next.php(51): Flarum\Http\Middleware\ProcessIp->process()
#51 /app/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(76): Laminas\Stratigility\Next->handle()
#52 /app/vendor/laminas/laminas-stratigility/src/MiddlewarePipe.php(65): Laminas\Stratigility\MiddlewarePipe->process()
#53 /app/vendor/laminas/laminas-httphandlerrunner/src/RequestHandlerRunner.php(96): Laminas\Stratigility\MiddlewarePipe->handle()
#54 /app/vendor/flarum/core/src/Http/Server.php(44): Laminas\HttpHandlerRunner\RequestHandlerRunner->run()
#55 /app/public/index.php(22): Flarum\Http\Server->listen()
#56 {main}
This only happens when SEO is disabled. Enabling it will fix the issue with Blog.
I think that this error was seen multiple times before (also on FreeFlarum), so you might already be familiar with the issue. But I'm leaving this here, in case you haven't found what causes it yet