Be sure to update
makeseeds.py to include the current version,
and remove old versions as necessary (at a minimum when GetDesirableServiceFlags
changes its default return value, as those are the services which seeds are added
to addrman with).
The seeds compiled into the release are created from sipa's DNS seed data, like this:
curl -s http://bitcoin.sipa.be/seeds.txt.gz | gzip -dc > seeds_main.txt python3 makeseeds.py < seeds_main.txt > nodes_main.txt python3 generate-seeds.py . > ../../src/chainparamsseeds.h
sudo apt-get install python3-dnspython