Lesser planar ally as a sorcerer?

[Velaryon]

Is there a way to get lesser planar ally (and thus qualify for thaumaturgist) as a sorcerer, preferably using methods that don't require the kind of cheese that DMs often ban?

[Crake]

arcane disciple for any one of the many domains that has lesser planar ally, and 14 wisdom

[Necroticplague]

Is there a way to get lesser planar ally (and thus qualify for thaumaturgist) as a sorcerer, preferably using methods that don't require the kind of cheese that DMs often ban?

Yes. Sorceror's aren't strictly requires to stay on the sorc/wiz list, so they can pick up some off list things. That could include planar ally, lesser.

[Darrin]

arcane disciple for any one of the many domains that has lesser planar ally, and 14 wisdom

Lust and Summoner domain, looks like. I think Summoner adds the most utility to a Sorcerer, assuming you haven't already selected the SM line as known spells.

Also: Planar Sorcerer sub level with Planar Touchstone/Touchstone, link to the Catalogues of Enlightenment, pick the Summoning domain and use the Higher Power to cast one of the domain spells.

[Crake]

Lust and Summoner domain, looks like. I think Summoner adds the most utility to a Sorcerer, assuming you haven't already selected the SM line as known spells.

Also: Planar Sorcerer sub level with Planar Touchstone/Touchstone, link to the Catalogues of Enlightenment, pick the Summoning domain and use the Higher Power to cast one of the domain spells.

Arcane disciple doesn't actually add all the spells in the domain to your spells known as a sorcerer, only to your spell list, allowing you to pick them as a spell when you choose new spells known, so picking a domain which has a lot of overlap with the sorcerer spell list is actually a bad idea. Celestial domain adds the most spells to your list, though it's heavily good themed, so that can be a problem.