I used to create my solr instance for drupal like this:
docker run -v $PWD/solrconf:/asdentcore -e SOLR_JAVA_MEM="-Xms2G -Xmx2G" --restart unless-stopped -p 8984:8983 -t --name asdentDevSolr -d solr:8.11
docker exec -it --user=solr asdentDevSolr bin/solr create_core -c asdentcore -d /asdentcore
Where ./solrconf contains the files from modules/contrib/search_api_solr/solr-conf-templates/7.x.
With the new 4.x branch of search_api_solr (and 8.x contents) I get
ERROR: Error CREATEing SolrCore 'asdentcore': Unable to create core [asdentcore] Caused by: solr.ICUCollationField
I've already tried https://stackoverflow.com/questions/53161034/solr-error-unable-to-create-core-mycore-caused-by-solr-icucollationfield - didn't help.
Container logs shows the following errors:
Caused by: org.apache.solr.common.SolrException: Unable to create core [asdentcore]
Caused by: org.apache.solr.common.SolrException: Could not load conf for core asdentcore: Can't load schema /var/solr/data/asdentcore/conf/schema.xml: Plugin init failure for [schema.xml] fieldType "collated_de": Error loading class 'solr.ICUCollationField'
Caused by: org.apache.solr.common.SolrException: Can't load schema /var/solr/data/asdentcore/conf/schema.xml: Plugin init failure for [schema.xml] fieldType "collated_de": Error loading class 'solr.ICUCollationField'
Caused by: org.apache.solr.common.SolrException: Plugin init failure for [schema.xml] fieldType "collated_de": Error loading class 'solr.ICUCollationField'
Caused by: org.apache.solr.common.SolrException: Error loading class 'solr.ICUCollationField'
Caused by: java.lang.ClassNotFoundException: solr.ICUCollationField