You need to be logged out of to start recovery process.

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3456188107

What counts as viable proof of ownership:
https://help.steampowered.com/en/faqs/view/40A0-8B4B-B54B-C51A

Steam Account Recovery

It is possible to recover a stolen Steam account. You don't need access to the email, phone or password currently tied to the stolen account for this to work.

The recovery process allows you to contact Steam Support to provide proof of ownership.

Follow this guide to recover your account:

https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3456188107

Support articles about account recovery:

Recovering a Stolen or Hijacked Steam Account

Providing Proof of Ownership

Link from the guide to start the recovery process:

https://help.steampowered.com/en/wizard/HelpWithLoginInfo?accountsearch=1&issueid=408&reset=1

crestzero12345 の投稿を引用：

i need help from anyone how can i recover my account

and dont name and shame against tos just report, block and move on