A DMR talkgroup is simply a way of grouping many Radio IDs into a single digital contact. Or put another way, a talkgroup is a method of organizing radio traffic specific to the DMR users that all want to hear the same thing and not be bothered by other radio traffic on a DMR network that they are not interested in hearing.
Talkgroups can exist for many purposes. You can have talkgroups for countries, states, counties, regions, cities, special interest groups etc. Just about any group of DMR users could have a talkgroup assigned to them if they wished to organize traffic that they can all monitor and take part in, without having to talk to each other one by one.
Talkgroups are also specific to individual DMR networks, BUT they all generally follow the same numbering scheme. So you need to make sure that you know what the various talkgroups are for each of the DMR networks that you may use.
reference from dmrfordummies.
Heard from Ailunce HD1 customers, the most used worldwide infrastructure network is Brandmeister and TGIF (which is mostly popular in US).
Find Brandmeister talkgroups here. https://brandmeister.network/?page=talkgroups and you can also download a Brandmeister talkgroups csv file from https://www.ailunce.com/Support/HD1/Codeplug, then you can import it into HD1 software.
Find TGIF talkgroups here. and you can find Ailunce talkgroup 888 there. http://tgif.network/talkgroups.php