Also being able to register a domain as an individual (I wanted to try ddns.com.au but their form seems to only accept entities with ABN?).

You need to be eligible to register a .com.au or .net.au domain, so you will need an ABN (even as an individual, i.e. sole trader).

You can register a .au domain without an ABN though.

From: https://www.auda.org.au/au-domain-names/domain-name-help/comau-and-netau-rules-eligibility-and-allocation

com.au and net.au Namespace

2.4.4 A Person applying for a Licence in the com.au and net.au Namespaces must be

• a Commercial Entity; and
• the domain name applied for must be:
  • (a) a Match of the Person’s company, business, statutory or Personal name; or
  • (b) an Acronym of the Person’s company, business, statutory or Personal name; or
  • (c) a Match of the Person’s Australian Trade Mark; or
  • (d) a Match to or an Acronym of a name of a Related Australian Body Corporate or
  • (e) a Match or an Acronym of a name of:
    • (i) a partnership of which the Person is a partner;
    • (ii) a trust of which the Person is a trustee; or
  • (f) a Match or Synonym of the name of:
    • (i) a Service that the Person provides;
    • (ii) Goods that the Person sells (whether retail or wholesale);
    • (iii) an event that the Person registers or sponsors;
    • (iv) an activity that the Person facilitates, teaches or trains;
    • (v) premises which the Person operates and which that Person is providing at the time of the application.

From: https://www.auda.org.au/policy/au-domain-administration-rules-licensing#2-4 :

.au direct Namespace

2.4.3 A Person applying for a Licence in the .au direct Namespace must have an Australian Presence, and .au direct Domain Names will be allocated according to the priority allocation process set out in the .au Direct Priority Rules.