R* has recently changed up their help site. Here are the new links -
(not making a different list/links for gta5/rdr2/etc - you can find)
If you need more / it isn't here - look directly - https://support.rockstargames.com/

Account Recovery - https://support.rockstargames.com/request/account/trouble-signing-into-your-account/account-recovery -In the past, they asked for various screenshots, info, and asked some questions to confirm you were the owner. Many users needed to look at their R* games on steam, and earliest achievement dates, compare them to purchase dates, to narrow down the 'social club linked to steam date'. Don't forget purchased R* games, linking, and possibly refunding too while digging for dates/info. Pay attention to date format as well. They may ask other questions.

*Depending 'when' you were compromised - you may even have an email from R* stating the email change, and it may have a link in it to recover the account yourself - provided it hasn't expired. The email may be in another language. At least, that is how it worked in the past ---- this may have changed. Also of note - if the 'old email' was used on a 'new social club account' (accidental, or on purpose) - the recover link won't work. You can only use an email on 1 social club account at a time. You would have to change THAT email on the 'new' social club account, before recovering with the link. Will update if I stumble on other info.

Lost access to email (deleted, dead, rotted, expired, forgot, etc) - https://support.rockstargames.com/request/account/trouble-signing-into-your-account/lost-access-to-my-email-account -Obviously, you can still try older devices, saved info in browsers, that slip of paper behind your desk, etc. The process here may be similar as above.

Forgot password - https://support.rockstargames.com/request/account/trouble-signing-into-your-account/forgotten-password -Of course, you just try to sign into the site - and stuff in all your email addresses, then check the inboxes if you 'forgot the email'.

2FA lost/missing/reset - https://support.rockstargames.com/request/account/trouble-signing-into-your-account/lost-or-missing-2-step-verification-authenticator
Not much to say here......

Deleted social club account and now have second thoughts? Catch it in time -
https://support.rockstargames.com/articles/6tcmzdH0xBfAFTbljDutcA/how-to-cancel-a-rockstar-games-account-deletion-request

You can also access ticket, livechat, and phonecallback from here 'usually' -
https://support.rockstargames.com/request/gta-v/activation-support/rockstar-games-activation-code-support/pc -Generally, you needed to be logged into 'an account' to access the livechat/callback. This is where people would create temporary/new social club accounts to access that. Some options turned off in past on weekends, holidays, etc.

In the past- support would sometimes go in circles if you spoke of unlinking while just trying to change email. If you are just trying to recover an account/change email - I'd steer from saying unlinking, as R* had/still has an unlinking process for disconnecting steam/egs from a social club account. At last check - you could not do this manually and needed their help. Putting the links here in case someone actually needs. In general though, if you can jump the hoops to 'unlink' --- you can simply recover access to your old account.
Unlinking -
https://support.rockstargames.com/articles/tp2PvsKT8MKjraByTigca/unlinking-an-account-from-your-rockstar-games-account
Unlinking Steam -
https://support.rockstargames.com/articles/1UjsMnPSkIDsNXlF8LRbKO/unlinking-your-steam-account-from-your-rockstar-games-account

For years R* has been helping people recover lost/compromised accounts. Under the old system/links- some did this in hours, others days/weeks, or never. Let's hope all thee new changes make this process easier in the future.
/goodluck

edit - and just because, a link to the 'old info' for nostalgia reasnons -.-
(and anything else pertinent in it that I forgot to post here)
https://gtm.steamproxy.vip/app/271590/discussions/0/3811787298086212982/#c3811787298086583512