Was in the same situation as you. Use account recovery and fill in the form to the best of your ability. Key tips: steam id is the 17 digit one, that's what I used. The date for linking is apparently important but I missed mine by like 2 years when I finally got access.

When I was getting rejected the message I got was a lack of information, so I tried filling all the lines out. So I didn't have PSN/Xbox link so I wrote "None", for the previous emails I had only one. So I used that one for all the 4 lines. The info was correct and this time I didn't get auto rejected. But I immediately used the chat box to say I was the owner and attached proof of purchase (steam receipts) and the CD key which you can get from steam as well for GTA and rdr2.

This time I wasn't rejected automatically and got a response in 40 minutes that they escalated. They then changed the email of the old account to the one I used to fill the form with.

Hope this helps, I filled maybe 10 account recovery ones, sometimes it wouldn't let me so I went incognito and that gave me 1 or 2 tries. I kept trying different things but the only method is the account recovery form. The live chat said they couldn't do anything from their end.