For postgres i do not see any problems. For postgis you need to read the changes, there are possible isues. But for a first try you can keep your postgis version.
- PostgreSQL 9.6.15 on x86_64-pc-linux-gnu (Ubuntu 9.6.15-1.pgdg16.04+1), compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609, 64-bit
- PostGIS lib version 2.3.3
and we want to upgrade to PostgreSQL 12.2.
Taking into account that there are three major versions between the source and the target, in addition to the PostGIS extension installed, is this upgrade possible?
It would be better to upgrade one version at a time?