I did emailed to Apple about this issue, and they agreed that it an iOS issue and also said that they dont any workaround for it.
So my guess is we need to wait for the official release which is very bad.
Below is the response from Apple
From: Apple Developer Technical Support dts@apple.com
Subject: Re: DTS Auto-Ack - I am unable to connect to bluetooth after updating my iOS to 15.1.
Follow-up: 784883575
Hello Vishwanath Kota,
Thanks for filing a Feedback Assistant report and attaching the sysdiagnose.
Although DTS is typically not able to provide any information about a specific Feedback Assistant report, I can say that it's normal for a Feedback Assistant report to be 'open' while an issue in iOS is being investigated. You should therefore expect the report's status to remain 'open' until this investigation is complete.
As my previous email also mentioned, it is normal and expected (unless additional information is required) that the submitter of a Feedback Assistant report will not receive a response to their submission. If additinonal information isn't required to investigate your report you should therefore not expect to receive a response to your submission.
In summary, the issue you've encountered appears to be a bug in iOS. It also appears that a work around is not possible.
Best regards,
Craig