Hi Balázs Rotár,
I understand how frustrating this is, especially since you’ve already enabled the Xbox privacy settings and tried the usual sign-in and Family group troubleshooting.
At this point, I suggest checking whether your Microsoft account’s date of birth/age classification is correct. If the account is still being treated as a child account, multiplayer permissions may remain restricted even though the visible privacy settings appear enabled.
If your account information is correct but Minecraft Java multiplayer is still disabled, please contact Xbox Support and ask them to check for any account-level age or multiplayer restrictions that may not be visible from your side.
Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas.
I hope this points you in the right direction.