SSH fingerprints(GitHub) differ when connecting to different routers

You can see that the two fingerprints differ, the second(PcziX…) is the legit that can be found here: https://help.github.com/en/github/authenticating-to-github/githubs-ssh-key-fingerprints

I couldn’t find anything about the first(nThbg6…) So, what changed between attempt 1 and 2?

Attempt 1: I setup an old router yesterday as a repeater with OpenWrt. It is connected with WiFi to the main router and with ethernet to my PC.

Attempt 2: Directly connect to router WiFi with my PC

attempt1:

▶ git push origin master The authenticity of host 'github.com (140.82.118.4)' can't be established. RSA key fingerprint is SHA256:PcziXGZE5iMp0Sm9dWn5qtfd/d7a+WOxIoQEL5pT33E. Are you sure you want to continue connecting (yes/no)? no Host key verification failed. fatal: Could not read from remote repository.  Please make sure you have the correct access rights and the repository exists. 

attempt2:

▶ git push origin master The authenticity of host 'github.com (140.82.118.4)' can't be established. RSA key fingerprint is SHA256:nThbg6kXUpJWGl7E1IGOCspRomTxdCARLviKw6E5SY8. Are you sure you want to continue connecting (yes/no)?  

I clean flashed the router yesterday and checked the checksum too.

Any ideas what’s going on?