apt warning: deb/dists/debian/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg)

[slrslr]

After upgrading Debian 11(oldstable) to Debian 12(stable), "sudo apt update" started complaining about:

SW: http://neilalexander.s3.dualstack.eu-west-2.amazonaws.com/deb/dists/debian/InRelease: Key is stored in legacy trusted.gpg keyring (/etc/apt/trusted.gpg), see the DEPRECATION section in apt-key(8) for details.

$ find /etc/apt -type f -iname *yggd*

/etc/apt/sources.list.d/yggdrasil.list
/etc/apt/sources.list.d/yggdrasil.list.save

$ grep -Ria yggd /etc/apt

/etc/apt/sources.list.d/yggdrasil.list:deb http://neilalexander.s3.dualstack.eu-west-2.amazonaws.com/deb/ debian yggdrasil
/etc/apt/sources.list.d/yggdrasil.list.save:deb http://neilalexander.s3.dualstack.eu-west-2.amazonaws.com/deb/ debian yggdrasil

$ sudo apt-key list
does not show anything that looks familiar and that i could remove (sudo apt-key del [KEYID]) and then try to obtain new key placing it in a correct location which may be /etc/apt/trusted.gpg.d/ ?

$ apt search yggdrasil

golang-github-arceliar-ironwood-dev/stable,stable 0.0~git20221115.ec61cea-1 all
  Routing library with public keys as addresses (library)

golang-github-yggdrasil-network-yggdrasil-go-dev/stable,stable 0.4.7-1 all
  Fully encrypted global-scale mesh network (library)

yggdrasil/unknown,now 0.5.8 amd64 [installed]
  Yggdrasil Network

yggdrasil-develop/unknown 0.5.8-16-g874083d amd64
  Yggdrasil Network

yggdrasil-vyos13/unknown 0.5.5 amd64

I see that https://yggdrasil-network.github.io/installation-linux-deb.html lists some Debian installation steps incl. key related.

Please what do you suggest to get rid of that apt warning and keep up to date?