I haven't been able to recreate the "could not settle on kex algorithm" using Bolt 5.5.0 from

debian:13

container running under Podman to Ubuntu 26.04 from images.linuxcontainers.org running under LXC. Everything just works:

# bolt command run -t ubuntu-2604.ark.keyhole.link --user root --password-prompt 'uptime'
Please enter your password:
CLI arguments ["user", "password"] might be overridden by Inventory: /root/boltproj/inventory.yaml [ID: cli_overrides]
Started on ubuntu-2604.ark.keyhole.link...
Finished on ubuntu-2604.ark.keyhole.link:
   14:54:26 up 3 min,  1 user,  load average: 0.09, 0.16, 0.22
Successful on 1 target: ubuntu-2604.ark.keyhole.link
Ran on 1 target in 0.46 sec

Do you have any customizations in `/etc/ssh/sshd_config`on the Ubuntu server that might be restricting the kex algorithms it will accept?