Is Oracle 18c XE good enough to start learning to be a DBA?
The "First Commandment" of any DBA is: Thou Shall Not Lose Data!

To accomplish this, you'll want to teardown, build, and restore/recover the database multiple times.  To that end, I'd recommend you use some sort of virtualization (eg Oracle VirtualBox).

You might be able to find both Oracle EE and MySQL pre-made virtual guests for VirtualBox.

I believe RMAN on XE is limited.  So, for backup/recovery practicing, I'd use EE.

Beyond that, any edition (of any RDBMS) would do.