Assuming the 'standard' config, ssl_access_log and ssl_request_log are written (in slightly different formats) for each HTTP request received on the TLS vhost. If the certificate is rejected, there is no TLS connection and it is not possible to send any HTTP request, so there is nothing to log.
Depending on the client program and TLS library it uses, it may ...
No, it is not logged on the server. This check is made on the client, there is no way to know for the server if this problem occured or not.
You can (and should) configure a default VirtualHost that catches all requests to domains not matching your "real" VirtualHosts. That way you can find out if requests to your server are made with other ...
Whilst I still haven't proven if <VirtualHost *:443> is actually working properly or not, I did still manage to solve the problem I was having by inserting my configuration for <VirtualHost *:443> outside of the tag. Maybe not a solution to my original question, but that's irrelevant now considering my ProxyPassReverse now works properly.
From what you've said your front end is hosted by Vercel, your back end by EC2. They're completely independent from a load balancing / certificate point of view.
Create a certificate for your back end server using AWS Certificate Manager (ACM). Alternately you can import an existing SSL cert into ACM, but then it won't re-issue automatically.
The OP chose not to post an answer, but did say that they solved the problem:
The problem was that there was were some strange domains added in the search part of /etc/resolve.conf on the host. And when I was trying to make a https request I have been redirected by DNS to some other server responding with plain http.
Correcting the DNS settings solved the ...
You're right that this represents a potential privacy concern: using SNI, the domain name is sent unencrypted.
That's why ESNI (Encrypted SNI) was proposed since by Cloudflare, who already implemented it in their CDN. At the time of this writing, browser support is close to zero, but this seems to be the future!