TLDR: This is a list (incomplete) of companies that advertise with Reddit and put money in its pockets, and some contact forms for popular companies.
Brilliant Earth (www.brilliantearth.com - scroll to bottom and choose contact method)
Universal Studios (https://www.universalstudios.com/contact/general-and-miscellaneous)
Microsoft
Focus Features
Mitsubishi Motors (https://www.mitsubishicars.com/contact-us)
IBM
Intuit
Autodesk
Electronic Arts
Ally Financial
Discover
Up Australia/Up Banking
ClearScore
Noosa Yoghurt (https://noosayoghurt.com/contact/)
BMW Mini Cooper
Adobe (https://www.facebook.com/Adobe/)
Adidas (https://www.facebook.com/adidas/)
Adrenaline Australia
GameStop (care@gamestop.com)
H&M (https://www.facebook.com/hm OR https://www.instagram.com/hm/)
Liquid I.V.
Oatly (https://www.oatly.com/contact OR https://www.facebook.com/Oatly/ OR https://www.instagram.com/oatly/)
JOE & THE JUICE (https://www.joejuice.com/contact)
Excedrin (https://www.excedrin.com/contact-us/)
Rayovac (https://www.rayovac.com/contact-us/)
Nespresso (https://www.facebook.com/nespresso/ OR https://www.instagram.com/nespresso/)
Novo Nordisk
BackMarket
Caliber Fitness (support@caliberstrong.com OR https://caliberstrong.com/contact-us/)
Lucozade (https://www.lucozade.com/support/)
Moen
Uber
HP
Tezos
Truebill
Ulta Beauty (https://www.ulta.com/guestservices/contact-us)
MeUndies (https://meundies.kustomer.help/contact/how-can-we-help-HyfOyZn0o)
Lagunitas
Aviva
Beyond Meat (https://www.beyondmeat.com/en-US/contact/)
Bitstamp (support@bitstamp.net)
Hootsuite
Zoetus
Wolt (https://explore.wolt.com/contact)
Fineco Bank
Alienware
Tails.com (https://shop.tails.com/contact-us/)
Duracell (https://www.duracell.com/en-us/contact/)
Creative Assembly/Total War: Warhammer III (https://www.totalwar.com/support/)
Finder Australia
Virgin Galactic
Bungie
Discover Financial Services
Capcom
Allergan Aesthetics Coolsculpting
Reddit has ads? lol block that shit.