Same problem here... I'm trying to upgrade from 2211.38 to 2211.42 and my only problem in the process is the upgrade from solr 9.7 to 9.8

Like your case, when I try to index solr in backoffice I'm having next error:

Unable to create core [master_xxx_Product_default] Caused by: solr.StempelPolishStemFilterFactory

Like the documentation says, I have removed the next tags from my solrcustom/server/solr/configsets/default/conf/solrconfig.xml:

<lib dir="${solr.install.dir:../../../..}/modules/analysis-extras/lib" regex=".*\.jar" />
<lib dir="${solr.install.dir:../../../..}/modules/hybris/lib" regex=".*\.jar" />

And i have this tag in solrcustom/server/solr/solr.xml:

<str name="modules">${solr.modules:analysis-extras,hybris}</str>

But the problem is not fixed. You mentioned that you had to change /core-customize/_SOLR_/server/solr/configsets/default/conf/solr.xml but, in my case, I only have schema.xml and solrconfig.xml in solrcustom/server/solr/configsets/default/conf