Welcome to the forum @chri-bra
Release: 2.0.6.1 (beta) 2021-05-03 note (also in About → Changelog) suggests:
The SSH backend has been updated
This update increases the security by prefering stronger encryption algorithms.
However, this can cause failing backups as the host key is reported as “changed”.
If this happens, edit the backup and update the host key.
You can find this option on Destination screen 2. Click x to delete previous value.
Next SFTP (SSH) access will ask you to accept the new value that it provides you.
Basically, this is like original setup that you would have done for your old fingerprint.
