I followed the guide Upgrade PostgreSQL Version in Ubuntu 20.04 | by Moorthiyuvaraj | YavarTechWorks | Medium to upgrade postgresql and now when I run SHOW server_version_num I get:
±---------------------+
| server_version_num |
|---|
| 120015 |
| ±---------------------+ |
I was able to upgrade to 8.0.1 now and it works!