After upgrading to 10.1 (thanks again to everyone who contributed!), I get lots of these messages in /var/log/httpd/error_log:
[Sun Sep 25 07:55:23.595498 2022] [proxy_fcgi:error] [pid 12089] [client 202.226.37.79:58248] AH01071: Got error 'Primary script unknown'
[Sun Sep 25 07:55:36.017873 2022] [proxy_fcgi:error] [pid 10274] [client 161.97.152.7:56272] AH01071: Got error 'Primary script unknown'
I have yet to spot if and where these messages actually point to something not working as expected.