I tried to connect to my server usingssh xxxx@xxxxxxx.xxxThe result was:Unable to negotiate with xxx.xxx.xxx.xxx port 22: no matching host key type found. Their offer: ssh-dssThen I ranssh xxxx@xxxxxxx.xxx -Gwith the outputuser xxxxhostname xxxxxxx.xxxport 22addressfamily anybatchmode nocanonicalizefallbacklocal yescanonicalizehostname falsechallengeresponseauthentication yescheckhostip yescompression nocontrolmaster falseenablesshkeysign noexitonforwardfailure nofingerprinthash SHA256forwardagent noforwardx11 noforwardx11trusted yesgatewayports nogssapiauthentication yesgssapidelegatecredentials nohashknownhosts yeshostbasedauthentication noidentitiesonly nokbdinteractiveauthentication yesnohostauthenticationforlocalhost nopasswordauthentication yespermitlocalcommand noprotocol 2proxyusefdpass nopubkeyauthentication yesrequesttty autorhostsrsaauthentication norsaauthentication yesstreamlocalbindunlink nostricthostkeychecking asktcpkeepalive yestunnel falseuseprivilegedport noverifyhostkeydns falsevisualhostkey noupdatehostkeys falsecanonicalizemaxdots 1compressionlevel 6connectionattempts 1forwardx11timeout 1200numberofpasswordprompts 3serveralivecountmax 3serveraliveinterval 0ciphers chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbchostkeyalgorithms ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsahostbasedkeytypes ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsakexalgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1loglevel INFOmacs umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1pubkeyacceptedkeytypes ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsaxauthlocation /usr/bin/xauthidentityfile ~/.ssh/id_rsaidentityfile ~/.ssh/id_dsaidentityfile ~/.ssh/id_ecdsaidentityfile ~/.ssh/id_ed25519canonicaldomainsglobalknownhostsfile /etc/ssh/ssh_known_hosts /etc/ssh/ssh_known_hosts2userknownhostsfile ~/.ssh/known_hosts ~/.ssh/known_hosts2sendenv LANGsendenv LC_*connecttimeout nonetunneldevice any:anycontrolpersist noescapechar ~ipqos lowdelay throughputrekeylimit 0 0streamlocalbindmask 0177I added my public key (from ~/.ssh/id_rsa.pub) to the ~/.ssh/authorized_keys file on the server (starting with ssh-rsa) which worked quite well at least until the last Ubuntu update (even today from a Linux Mint machine - different key, but also rsa).On the Ubuntu I'm using OpenSSH_7.2p2 Ubuntu-4ubuntu1, OpenSSL 1.0.2g-fips  1 Mar 2016 (I don't know the ssh version from the Mint machine; the server runs CentOS, i think)What am I doing wrong?Just for fun I added:# http://www.openssh.com/legacy.htmlHost xxxxxxx.xxx    HostkeyAlgorithms +ssh-dssto the .ssh/config.The connection is successful, but then I have to type my password all the time, since the ~/.ssh/authorized_keys does not have a public dsa key.So why does ssh using RSA does not work from my Ubuntu 16.04 LTS machine?
Why is it not possible to connect to my server using RSA from an Ubuntu machine?
ubuntu;ssh;openssh