Macports mod_proxy configuration gives error AH01144 No protocol handler was valid for the URL .. scheme http

I am trying to a reverse proxy to get Apache Jena Fuseki which will only work on localhost:3030 visible from my intranet. I get the error message shown below although the proxy modules seem to be enabled.
The hints in

• https://stackoverflow.com/questions/23931987/apache-proxy-no-protocol-handler-was-valid

did not help me e.g. activating mod_ssl did not make a difference and there seem to be too many modules to choose from so that try and error might get very tedious.

The webserver runs properly and serves index.html o.k. The /jena proxy redirect leads to the error.

How could this problem be fixed?

etc/apache2/extra/httpd-vhosts.conf

<VirtualHost *:80>
    ServerAdmin webmaster@bitplan.com
    ServerName jena.zeus.bitplan.com
    ServerAlias wikdata.zeus.bitplan.com
    ProxyPreserveHost On
    ProxyRequests Off
    # allow queries to run up to two hours
    ProxyPass /jena http://localhost:3030/ connectiontimeout=10 timeout=7200
    ProxyPassReverse /jena http://localhost:3030/
    ErrorLog "/private/var/log/apache2/jena-error_log"
    CustomLog "/private/var/log/apache2/jena-access_log" common
</VirtualHost>

error message:
/var/log/apache2/jena-error.log

[Fri Sep 11 09:11:41.660860 2020] [proxy:warn] [pid 61446] [client ...:59602] AH01144: No protocol handler was valid for the URL /jena (scheme 'http'). If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.

apachectl -S

apachectl -S
VirtualHost configuration:
*:80                   jena.zeus.bitplan.com (/opt/local/etc/apache2/extra/httpd-vhosts.conf:11)
ServerRoot: "/opt/local"
Main DocumentRoot: "/opt/local/www/apache2/html"
Main ErrorLog: "/var/log/apache2/error_log"
Mutex default: dir="/opt/local/var/run/apache2/" mechanism=default 
Mutex mpm-accept: using_defaults
Mutex proxy: using_defaults
PidFile: "/opt/local/var/run/apache2/httpd.pid"
Define: DUMP_VHOSTS
Define: DUMP_RUN_CFG
User: name="_www" id=70
Group: name="_www" id=70

apachectl -M

apachectl -M
Loaded Modules:
 core_module (static)
 so_module (static)
 http_module (static)
 mpm_prefork_module (static)
 authn_file_module (shared)
 authn_core_module (shared)
 authz_host_module (shared)
 authz_groupfile_module (shared)
 authz_user_module (shared)
 authz_core_module (shared)
 access_compat_module (shared)
 auth_basic_module (shared)
 reqtimeout_module (shared)
 filter_module (shared)
 xml2enc_module (shared)
 proxy_html_module (shared)
 mime_module (shared)
 log_config_module (shared)
 env_module (shared)
 headers_module (shared)
 setenvif_module (shared)
 version_module (shared)
 proxy_module (shared)
 proxy_connect_module (shared)
 slotmem_shm_module (shared)
 unixd_module (shared)
 status_module (shared)
 autoindex_module (shared)
 dir_module (shared)
 alias_module (shared)

relevant httpd.conf changes

rcsdiff httpd.conf
===================================================================
RCS file: RCS/httpd.conf,v
retrieving revision 1.1
diff -r1.1 httpd.conf
109,110c109,110
< #LoadModule xml2enc_module lib/apache2/modules/mod_xml2enc.so
< #LoadModule proxy_html_module lib/apache2/modules/mod_proxy_html.so
---
> LoadModule xml2enc_module lib/apache2/modules/mod_xml2enc.so
> LoadModule proxy_html_module lib/apache2/modules/mod_proxy_html.so
125,126c125,126
< #LoadModule proxy_module lib/apache2/modules/mod_proxy.so
< #LoadModule proxy_connect_module lib/apache2/modules/mod_proxy_connect.so
---
> LoadModule proxy_module lib/apache2/modules/mod_proxy.so
> LoadModule proxy_connect_module lib/apache2/modules/mod_proxy_connect.so
291c291
< ErrorLog "var/log/apache2/error_log"
---
> ErrorLog "/var/log/apache2/error_log"
320c320
<     CustomLog "var/log/apache2/access_log" common
---
>     CustomLog "/var/log/apache2/access_log" common