Hey,
I just upgraded to Nexus 3.83.0 and ran into an issue. It seems like the new license system, cause downgrading to OSS to not work anymore. I followed the instructions within https://support.sonatype.com/hc/en-us/articles/115015608967-How-to-downgrade-from-Nexus-3-Pro-to-Nexus-3-OSS-or-Community-Edition-CE to downgrade to Nexus OSS in an older version. When I started Nexus 3.83.0 it showed up as Pro version in the upper left Logo and I was prompted to upload a license.