To help (or push) users to use Teams rather than Skype it is possible to remove the "New Skype Meeting" button, from the Outlook client, so users will use the "New Teams Meeting" button to schedule new online meetings.

The option needs to be enabled in Teams Meeting policies using PowerShell. The following script contains the commands for making the modifications:

# Teams Meeting Policy set PrefferredMeetingProviderForIslands

# Connect to Skype Online
Import-Module SkypeOnlineConnector
$Session = New-CsOnlineSession
Import-PSSession $Session -AllowClobber

# Get individual users and list username and meeting policy. If blank then uses default meeting policy
get-csonlineuser -identity [email protected] | select userprincipalname, teamsmeetingpolicy

# Get all users and list username and meeting policy. If blank then uses default meeting policy
get-csonlineuser | select userprincipalname, teamsmeetingpolicy

# Set Button in Outlook to Teams Only for meeting policy. Change back using value TeamsAndSfb
Set-CsTeamsMeetingPolicy -identity "Skype Meetings Button Disabled" -PreferredMeetingProviderForIslands Teams

# Set on all existing policies
Get-CsTeamsMeetingPolicy | foreach { Set-CsTeamsMeetingPolicy -Identity $_.Identity -PreferredMeetingProviderForIslands Teams } 

# Set Button in Outlook to Teams Only for all meeting policies. Change back using value TeamsAndSfb
Get-CsTeamsMeetingPolicy | Set-CsTeamsMeetingPolicy -PreferredMeetingProviderForIslands Teams

# Set Meeting Policy for an individual user
Grant-CsTeamsMeetingPolicy -Identity "[email protected]" -PolicyName "Skype Meetings Button Disabled"

I would recommend creating a new Teams meeting policy to test before updating existing meeting policies.