Is there a list of new features in 4.81?

New in v4.81, December 2022
Version 4.81 corrects a number of problems in v4.80, in particular a bug that could result in user wordlists being lost from the spelling checker. As well, it implements two significant new capabilities:
Support for Gmail OAUTH2 The program now has full support for the OAUTH2 authentication mechanism as implemented and required by Gmail, and can be configured for Gmail use with only a couple of clicks. That sentence can't possibly convey how much time and effort went into this one feature, but there is no doubt that it is important and worthwhile.
Format selection for copies to self The program now allows you to choose how your copies to self are saved - in reloadable format (for easy re-sending), in final format (for accurate display and preservation of attachments), or in both formats. See the 'Copies to self' preference page for this setting.

That is from help - what is new in this verion.

Are there instructions on how to configure it for OAUTH2?

Yes.

OAUTH2 is for GMail only. There is a new button titled 'GMail' in the General tab of internet options. There are a couple of well explained options but most everything is automated. You will be prompted to login to Google which then generates authentication credentials that you can't change. The resulting .pnd files do not contain a username or password entry.

One thing to be aware of is that GMail OAUTH2 creations process is identity specific in that if you have an identity from which you POP and send mail using your GMail account then you must 'be' the identity when you setup OAUTH2. If you don't, the process completes successfully but then won't work. Note: you do not have to become that identity to check mail. The issue is only during OAUTH2 creation. Checking mail for multiple identities is not affected.

My email provider is google workplaces. I use POP. I have several computers one of which is where all my emails are stored. Before the OAUTH setup I used the recent feature in Pegasus on the other computers to prevent emails from being deleted on the gmail pop server. In 4.81 I don't see a way to do this.

I am unsure about what you are asking. The option to leave mail on the server has been in Pegasus Mail for as long as I can remember so is not a recent feature. It did not change between 4.80 and 4.81. It is still in the General tab of the POP3 host configuration. If you created an OAUTH2 one, the host name will be suffixed with (OAUTH2). Select it then click the edit button to get to its configuration. Nothing has changed in there other than the username and password fields being disabled. The "Delete mail on server..." option is in the lower part of the General tab.