-----BEGIN CERTIFICATE-----
MIIOSTCCDTGgAwIBAgIQFHitMmJOwc0JhD4dXvgHZTANBgkqhkiG9w0BAQsFADA7
...
-----END CERTIFICATE-----
You can verify contents of a public certificate from a console: openssl x509 -in certificate.crt -text -noout
or using a website: https://www.sslshopper.com/certificate-decoder.html
The certificate
Give it a go, if you have any troubles I am more than happy to assist. (edited)s3drive.app
as it is or replace it with anything else, but in principle such corporate proxy would replace any SSL certificate to its own.
openssl s_client -showcerts -connect s3drive.app:443 < /dev/null 2> /dev/null | sed -n '/^-----BEGIN CERT/,/^-----END CERT/p'
This command will result in one or more certificate. Use first only if it's the only one, otherwise either use second or last one. (I haven't tried myself and I am not sure if intermediary CA or root CA is needed)
TLS1.3 isn't needed.
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It may well be that your S3 destination/endpoint doesn't have a publicly trusted SSL certificate, in such case you either need to make sure that is using trusted SSL certificate ... or you can trust it yourself by importing its root CA using the methods above (either through Chrome or command line).
Did you try extracting the CA and importing it into S3Drive?
If you don't mind telling, please let me know where are you trying to connect. (edited)