"File schema_extra_types.xml could not be fetched" warning on fresh Solr 8.8.0 install

I have same error
Drupal 10.3
drupal-4.3.4-solr-8.x-0
Solr 8.11.3

What's wrong?

File schema_extra_fields.xml could not be fetched from Solr server for validation: Solr endpoint http://solr_container:8983/ internal Solr server error (code: 500, body: { "responseHeader":{ "status":500, "QTime":2}, "error":{ "metadata":[ "error-class","org.apache.solr.common.SolrException", "root-error-class","java.lang.NullPointerException"], "trace":"org.apache.solr.common.SolrException\n\tat org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:236)\n\tat org.apache.solr.core.SolrCore.execute(SolrCore.java:2637)\n\tat org.apache.solr.servlet.HttpSolrCall.execute(HttpSolrCall.java:791)\n\tat org.apache.solr.servlet.HttpSolrCall.call(HttpSolrCall.java:564)\n\tat org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:427)\n\tat org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:357)\n\tat org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:201)\n\tat org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1601)\n\tat org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:548)\n\tat org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:143)\n\tat org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:600)\n\tat org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127)\n\tat org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:235)\n\tat org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1624)\n\tat org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:233)\n\tat org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1434)\n\tat org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:188)\n\tat org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:501)\n\tat org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1594)\n\tat org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:186)\n\tat org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1349)\n\tat org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)\n\tat org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:191)\n\tat org.eclipse.jetty.server.handler.InetAccessHandler.handle(InetAccessHandler.java:177)\n\tat org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:146)\n\tat org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127)\n\tat org.eclipse.jetty.rewrite.handler.RewriteHandler.handle(RewriteHandler.java:322)\n\tat org.eclipse.jetty.server.handler.gzip.GzipHandler.handle(GzipHandler.java:763)\n\tat org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:127)\n\tat org.eclipse.jetty.server.Server.handle(Server.java:516)\n\tat org.eclipse.jetty.server.HttpChannel.lambda$handle$1(HttpChannel.java:400)\n\tat org.eclipse.jetty.server.HttpChannel.dispatch(HttpChannel.java:645)\n\tat org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:392)\n\tat org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:277)\n\tat org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:311)\n\tat org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105)\n\tat org.eclipse.jetty.io.ChannelEndPoint$1.run(ChannelEndPoint.java:104)\n\tat org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.runTask(EatWhatYouKill.java:338)\n\tat org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:315)\n\tat org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.tryProduce(EatWhatYouKill.java:173)\n\tat org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:131)\n\tat org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:409)\n\tat org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:883)\n\tat org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1034)\n\tat java.base/java.lang.Thread.run(Unknown Source)\nCaused by: java.lang.NullPointerException\n\tat org.apache.solr.handler.admin.ShowFileRequestHandler.getAdminFileFromFileSystem(ShowFileRequestHandler.java:361)\n\tat org.apache.solr.handler.admin.ShowFileRequestHandler.showFromFileSystem(ShowFileRequestHandler.java:201)\n\tat org.apache.solr.handler.admin.ShowFileRequestHandler.handleRequestBody(ShowFileRequestHandler.java:145)\n\tat

I have this too.

Drupal 10.3.6, search_api_solr 4.3.5, Solr 9.7.0.

I am having the same 500 response from Solr. Indexing and search are working as expected.

solr 9.4
drupal 9.5.11
seach_api_solr 4.3.1

I have the same problem with Drupal 10.3, search_api_solr 4.3.5 and solr 9.7

schema_extra_types.xml belongs to the search_api_solr config-set.

It could be that you made a mistake in the setup and you're running the default managed schema of Solr instead of the one that belongs to this module.

If indexing and searching "works", it doesn't mean that it really works. The default managed schema simply accepts any field name using a simple default string type. So a lot of features don't work as they should, for example language-specific full text searches.
you just don't get errors, but the search results are very bad. You might not notice it directly if your content is in English.

The default schema would trigger an error if the wrong schema.xml was there. The correct schema is being read and it exists in the same location as this file.