Also, self-described scrapper Dane Sweeny battled his way into the main draw while fellow local hope Storm Hunter completed a return after serious injury.
With the four qualifiers sealing their berths on Thursday, there are 21 Australians - 11 men and 10 women - across the two main draws.
Kubler had fought back from a set down against Alexander Blockx before the German retired when the Australian was leading 3-6 6-3 1-0.
In his first main draw since 2024, Kubler's reward is a daunting first-round match-up with world No.29 Francis Tiafoe - and if he passes that, potentially a third-round clash with top-billed Australian Alex de Minaur.
Inglis, who beat Germany's Tamara Korpatsch 6-4 6-4 after falling short in the final qualifying match in 2024 and 2025, will take on a familiar face in fellow Australian Kimberly Birrell in the first round.
Cheered on by a court packed with vocal home fans, 24-year-old Sweeny overcame Italy's Stefano Travaglia 7-6 (7-5) 7-6 (7-3) to qualify for the Open for just the second time, following his 2024 campaign.
Sweeny will go toe-to-toe with evergreen French veteran Gael Monfils.
The Australian made a first-round exit at what was his only previous appearance at a major, and is currently ranked No.182 in the world.
Former doubles world No.1 Hunter downed American Taylor Townsend 7-6 (8-6) 6-2 and will face Spaniard Jessica Bouzas Maneiro in the first round.
After Thursday's win, an emotional Sweeny sat court-side with his head in his hands, soaking up his achievement.
"I'm in disbelief," he said.
"Really, I was ranked 700 not so long ago, and I persevered, I was doubting the whole time.
"I just feel so incredibly grateful to be able to be in this position, and I'm proud of myself for digging in there when it was really tough.
"So I can't really believe it yet, but I'm super excited."
The diminutive Sydneysider, who only weighs 63kg and stands 170cm, threw himself into every point in a stunning acrobatic display that often ended with him splayed across the court.
It appeared he had injured his wrist in the second set while diving for a shot, but he shook it off and played on.
Hunter is looking to repeat her 2024 Open performance, when she won through qualifying and then advanced through to the third round.
The 31-year-old ruptured her achilles a few months later in April 2024 and has been on the comeback trail since.
Hunter served for the first set but Townsend, also a former doubles world No.1, pounded a backhand winner and then levelled at 6-6 before the Australian took the tie-break 8-6.
Hunter broke her 11th-seeded rival and then went up 4-2, and with three match points, sealed the win with an ace.
