To get rid of 128 bit encryption I had to disable
ECDHE-RSA-AES128-GCM-SHA256
But then I got error messages from the popular browsers Server negotiated HTTP/2 with blacklisted suite. That is caused by DHE-RSA-AES256-SHA and ECDHE-RSA-AES256-SHA
With a lof of trial and error I came to the following
Listen 443
<If "%{SERVER_PORT} == '443'">
<IfModule mod_headers.c>
Header always set Strict-Transport-Security "max-age=15553000; preload"
</IfModule>
</If>
ProtocolsHonorOrder On
Protocols h2c h2 http/1.1
SSLUseStapling off
SSLSessionCache shmcb:/opt/apache2/logs/ssl_gcache_data(512000)
SSLOptions +StrictRequire +StdEnvVars -ExportCertData
SSLProtocol -all +TLSv1 +TLSv1.1 +TLSv1.2
SSLCompression Off
SSLHonorCipherOrder On
SSLCipherSuite ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-SHA384:DHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES256-SHA256
However that has the negative effect that Android smaller than 7 and smaller than IE 11 can’t connect to the server. Also some older Firefox versions can’t connect. Depending on the application it might be worth to use such a config that doesn’t allow 128 bit encrypted connections.