We're running 11.1.0 Umbraco version. The issues are that user with apostrophe in email can't register, and those already in database can't change password (returns following error:Invalid UserName). It doesn't seem to have any issues assigning values to properties (e.g. Password reset token). MemberService and MemberManager both seem to be able to retrieve member using said invalid email without a problem. Is there anything we can do to avoid or fix these issues or should we submit this issue on Github and wait for it to get fixed?

You should submit it as an issue

I've created issue on Github https://github.com/umbraco/Umbraco-CMS/issues/15814 is it possible to get any estimate when this could be fixed?