portainer: 2.6.0 => [err: Cannot connect to the Docker daemon at tcp://tasks.agent:9001. Is the docker daemon running?]

Bug description

After upgrading from Ubuntu 20.04 to 21.04 and upgrading Portainer from 2.5.x to 2.6.0 I canot see the (cluster) related docker data anymore. Also the agents are updated.

Resolving is fine.

I cannot see anything from containers to networks, nothing but the swarm page is fine and everything is active and up.

Expected behavior

Seeing my stacks/services/containers/networks

Portainer Logs

Potainer: portainer_portainer.1.ylrk7fhrtryb@docker-01.mydomain.tld | 2021/06/30 00:28:17 [WARN] [docker,snapshot] [message: unable to snapshot engine information] [endpoint: primary] [err: Cannot connect to the Docker daemon at tcp://tasks.agent:9001. Is the docker daemon running?]

Agent: portainer_agent.0.j6etvn5ojxt2@docker-01.mydomain.tld | 2021/06/30 00:31:17 http: superfluous response.WriteHeader call from github.com/portainer/libhttp/error.writeErrorResponse (error.go:37)

Technical details:

• Portainer version: 2.6.0
• Docker version (managed by Portainer):

# docker version
Client: Docker Engine - Community
 Version:           20.10.7
 API version:       1.41
 Go version:        go1.13.15
 Git commit:        f0df350
 Built:             Wed Jun  2 11:56:38 2021
 OS/Arch:           linux/amd64
 Context:           default
 Experimental:      true

Server: Docker Engine - Community
 Engine:
  Version:          20.10.7
  API version:      1.41 (minimum version 1.12)
  Go version:       go1.13.15
  Git commit:       b0f5bc3
  Built:            Wed Jun  2 11:54:50 2021
  OS/Arch:          linux/amd64
  Experimental:     false
 containerd:
  Version:          1.4.6
  GitCommit:        d71fcd7d8303cbf684402823e425e9dd2e99285d
 runc:
  Version:          1.0.0-rc95
  GitCommit:        b9ee9c6314599f1b4a7f497e1f1f856fe433d3b7
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

• Platform (windows/linux): Ubuntu 21.04
• Browser: All
• Use Case (delete as appropriate): Using Portainer test env
• Have you reviewed our technical documentation and knowledge base? Yes

Additional contextd0o None