v20 is still in beta, so the 3CX website still only offers v18 for install. I do have the following .NET versions installed + the older cores (2.0, 3.0, 3.5, 4.0). Am still getting the same error at the end after trying to install.
v2.0.50727
1028
1029
1030
1031
1032
1033 2.0.50727.4927 SP2
1035 2.0.50727.4927 SP2
1036 2.0.50727.4927 SP2
1038 2.0.50727.4927 SP2
1040 2.0.50727.4927 SP2
1041 2.0.50727.4927 SP2
1042 2.0.50727.4927 SP2
1043 2.0.50727.4927 SP2
1044 2.0.50727.4927 SP2
1045 2.0.50727.4927 SP2
1046 2.0.50727.4927 SP2
1049 2.0.50727.4927 SP2
1053 2.0.50727.4927 SP2
1055 2.0.50727.4927 SP2
2052 2.0.50727.4927 SP2
2070 2.0.50727.4927 SP2
3076 2.0.50727.4927 SP2
3082 2.0.50727.4927 SP2
v3.0
v3.0
v3.0 3.0.30729.4926
v3.5
1033 3.5.30729.4926 SP1
v4.0
Client 4.0.0.0
Microsoft.NETCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 6.0.31 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.6 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 6.0.31 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.6 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
--------------------------------------------------------
MSI (s) (E4:68) [10:01:47:243]: Executing op: ActionStart(Name=InstallPostgresService,,)
MSI (s) (E4:68) [10:01:47:243]: Executing op: CustomActionSchedule(Action=InstallPostgresService,ActionType=3090,Source=C:\Program Files\3CX Phone System\Bin\pgsql\bin\pg_ctl.exe,Target=register -N "3CX PhoneSystem Database Server" -U .\LocalSystem -P EF11C93F-3E70-4D6E-A2C9-AC87944EC028 -D "C:\Program Files\3CX Phone System\Data\DB",)
CustomAction InstallPostgresService returned actual error code -1073741515 (note this may not be 100% accurate if translation happened inside sandbox)
MSI (s) (E4:68) [10:01:47:617]: Note: 1: 1722 2: InstallPostgresService 3: C:\Program Files\3CX Phone System\Bin\pgsql\bin\pg_ctl.exe 4: register -N "3CX PhoneSystem Database Server" -U .\LocalSystem -P EF11C93F-3E70-4D6E-A2C9-AC87944EC028 -D "C:\Program Files\3CX Phone System\Data\DB"
MSI (s) (E4:68) [10:01:52:414]: Product: 3CX Phone System -- Error 1722. There is a problem with this Windows Installer package. A program run as part of the setup did not finish as expected. Contact your support personnel or package vendor. Action InstallPostgresService, location: C:\Program Files\3CX Phone System\Bin\pgsql\bin\pg_ctl.exe, command: register -N "3CX PhoneSystem Database Server" -U .\LocalSystem -P EF11C93F-3E70-4D6E-A2C9-AC87944EC028 -D "C:\Program Files\3CX Phone System\Data\DB"