Hi @dmenne,
You can do it the same way as /stats just add one line for /.well-known/acme-challenge
ProxyPass /stats !
ProxyPass /.well-known/acme-challenge !
So requests to validate your domain will use the defined DocumentRoot in your VirtualHost conf instead of proxying it.
If you are not using a DocumentRoot for your VirtualHost you could even specify an Alias to point these requests to a concrete dir (in below example the dir is /var/www/html/letsencrypt/) .
Alias "/.well-known/acme-challenge/" "/var/www/html/letsencrypt/.well-known/acme-challenge/"
You could put this Alias before <Proxy *> but if you already have a working DocumentRoot no need for this Alias.
I hope this helps.
Cheers,
sahsanu