General:
Know both Jira/Confluence on admin level:
Understand user management (directories, users, groups), permissions, worklows (conditions, validators, post-functions), screens, fields, schemes, project management, boards (dashboards, agile boards, filters), licensing, add-ons (most popular ones), etc
Key differences between 3 deployment types: cloud, server, data center
Backend:
Basic: know the basic structure of applications: install dirs, data dirs, main config files
Preferred: able to install/configure apps from scratch, includes: downloading and installing app and java binaries, installing and configuring mysql/psql, running the apps and connecting to database
Advanced: able to upgrade applications to next version; migrate apps to new servers; ZDU upgrades; server to DC; do all this in AWS
OS:
Linux is a must, at least basic knowledge of how to navigate, copy/move files and dirs, edit config files, start/stop services and processes, tail logs, etc
DB:
Preferred, but at the very least basic knowledge how to connect to mysql/psql and run queries
Comms:
Most work is client-facing: ability to explain what/when/how/why in semi-technical terms; BS your way out of situations where you don't know
Not too technical options (sans backend/OS/DB):
Atlassian admin - still need to know all the general stuff (this might be the best option if you don't have technical skills)
Cloud migrations - don't need too much technical backend experience, but need to know the core differences between onprem vs cloud, migration methods, user management, and ability to execute them
3rd party migrations - basic knowledge of linux; expert knowledge of excel - able to manipulate and transform CSV data; good knowledge of Jira configs.