SSH, deprecated RSA-SHA1

I realised today I can't log in on the home router anymore.  SSH just says

	Permission denied (publickey).

But using the `-v` flag I could see the debug message:

	debug1: send_pubkey_test: no mutual signature algorithm

A quick web search later revealed that the problem is due to RSA SHA1
being deprecated.  These days all my keys are of the ed25519 type,
except for a few old keys that I did not rotate quite yet.

My home router does not allow password-based login.  In order to ssh
on it and install a new ed25519 key, I had to temporarily override
the deprecation:

  ssh -o PubkeyAcceptedKeyTypes=+ssh-rsa ...

EDIT: Some time later, this doesn't work anymore.  The following will:

  ssh -o PubkeyAcceptedAlgorithms=+ssh-rsa -o HostKeyAlgorithms=+ssh-rsa