I've added my comment to upstream here:
romanz#387 (comment)
But decided to create this issue so we can keep track of it, the failure is:
File "/usr/lib/python3.9/site-packages/libagent/ssh/protocol.py", line 148, in sign_message
signature = self.conn.sign(blob=blob, identity=key['identity'])
File "/usr/lib/python3.9/site-packages/libagent/ssh/init.py", line 246, in sign
return conn.sign_ssh_challenge(blob=blob, identity=identity)
File "/usr/lib/python3.9/site-packages/libagent/ssh/client.py", line 35, in sign_ssh_challenge
msg = parse_ssh_blob(blob)
File "/usr/lib/python3.9/site-packages/libagent/ssh/client.py", line 84, in parse_ssh_blob
assert not i.read()
AssertionError
sign_and_send_pubkey: signing failed for ED25519 "/tmp/trezor-ssh-pubkey-xvuheqx8" from agent: communication with agent failed