It's between 5-6% per energy. Tracked data here: https://www.reddit.com/r/SWGalaxyOfHeroes/comments/jbah33/gl_tickets_farming_data_v2/
Call it 5% for easy maths. On the 10 energy Kyrotech node (probably the best bet, as you'll need tons) that's 50% chance. You need 420 tickets (assuming no failures) to unlock a GL. 840 attempts, 8,400 energy required.
You get 375 free energy a day, plus 3 x 120 in refreshes = 735 energy a day.
8,400 / 735 = 11.4 days.
Using the same maths tiers 4, 5 and unlocking the Ultimate from ten attempts at tier 6 should take a further 22/23 days.
