There is no way you can populate that value {!Community_URL} . .So i would suggest to create Label and store the community url value there, then refer that Label to your email template.
There is no way you can populate that value {!Community_URL} . .So i would suggest to create Label and store the community url value there, then refer that Label to your email template.
All Answers
String ntwrkId = Network.getNetworkId();
ConnectApi.Community comm = ConnectApi.Communities.getCommunity(ntwrkId);
System.debug(comm.siteUrl);
Please mark it best if it helps you.
Regards,
Pawan Kumar
Cheers!