OR
Try it this way:
#skip challenge requests and
<LocationMatch "^/(?!\.well-known)">
#send all other requests to HTTPS
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^/?(.*) https://%{SERVER_NAME}/$1
</LocationMatch>
<Location /.well-known/acme-challenge/>
DocumentRoot /var/lib/letsencrypt/http_challenges
</Location>