verified successfully on hirsute-proposed:

root@h1:~# apt policy heat-dashboard-common                                                                                                                                                   
heat-dashboard-common:                                                                                                                                                                        
  Installed: (none)                                                                                                                                                                           
  Candidate: 5.0.0-0ubuntu2                                                                                                                                                                   
  Version table:                                                                                                                                                                              
     5.0.0-0ubuntu2 500                                                                                                                                                                       
        500 http://archive.ubuntu.com/ubuntu hirsute-proposed/main amd64 Packages                                                                                                             
     4.1.0-0ubuntu1 500                                                                                                                                                                       
        500 http://archive.ubuntu.com/ubuntu hirsute/main amd64 Packages                                                                                                                      
root@h1:~# apt policy heat-dashboard-common python3-heat-dashboard                                                                                                                            
heat-dashboard-common:                                                                                                                                                                        
  Installed: (none)                                                                                                                                                                           
  Candidate: 5.0.0-0ubuntu2                                                                                                                                                                   
  Version table:                                                                                                                                                                              
     5.0.0-0ubuntu2 500                                                                                                                                                                       
        500 http://archive.ubuntu.com/ubuntu hirsute-proposed/main amd64 Packages                                                                                                             
     4.1.0-0ubuntu1 500                                                                                                                                                                       
        500 http://archive.ubuntu.com/ubuntu hirsute/main amd64 Packages                                                                                                                      
python3-heat-dashboard:                                                                                                                                                                       
  Installed: (none)                                                                                                                                                                           
  Candidate: 5.0.0-0ubuntu2                                                                                                                                                                   
  Version table:                                                                                                                                                                              
     5.0.0-0ubuntu2 500                                                                                                                                                                       
        500 http://archive.ubuntu.com/ubuntu hirsute-proposed/main amd64 Packages                                                                                                             
     4.1.0-0ubuntu1 500                                                                                                                                                                       
        500 http://archive.ubuntu.com/ubuntu hirsute/main amd64 Packages        
                                                                                                              
root@h1:~# sudo apt install python3-heat-dashboard --yes
...

root@h1:~# apt policy python3-heat-dashboard heat-dashboard-common
python3-heat-dashboard:
  Installed: 5.0.0-0ubuntu2
  Candidate: 5.0.0-0ubuntu2
  Version table:
 *** 5.0.0-0ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu hirsute-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     4.1.0-0ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu hirsute/main amd64 Packages
heat-dashboard-common:
  Installed: 5.0.0-0ubuntu2
  Candidate: 5.0.0-0ubuntu2
  Version table:
 *** 5.0.0-0ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu hirsute-proposed/main amd64 Packages
        100 /var/lib/dpkg/status
     4.1.0-0ubuntu1 500
        500 http://archive.ubuntu.com/ubuntu hirsute/main amd64 Packages