It has always been a bit of an Achilles heel with INAV that any of the autonomous flight modes including Return To Home required an active working compass to be connected to the FC. Well with the release of INAV 7.1 this is no longer the case. You can use all autonomous flight modes without a compass. This is achieved with the use of some clever new sensor fusion logic in INAV 7.1 which is able to determine the heading of the quad without the use of a compass. See Pawel's video below for a demonstration.

Pawel mentions at the end of the video that a compass is still required to initially set up INAV after which the compass can then be disabled, but someone in the comments has pointed out that you don't to do that and can just set the compass type to "FAKE" which will then let you configure the autonomous navigation modes after which you can then disable the fake compass completely.

this is great! now i can finally fly my drone with li-ion battery which didn't work before because the steel shells of its cells disturbed my magnetometer which isn't on a pole. time to update inav after some years. do you know if it is possible top put the magnetometer on a switch so i could switch it off and on?

I would make an intelligent guess that the magnetometer function can't be switched on and off during flight. I can't think of any viable use case for switching it on and off on-the-fly while your aircraft is already in the air. If you have a working calibrated magnetometer then you might as well just use it because it will make the flight modes more accurate. If you already have a magnetometer wired up but it is causing too many issues then just leave it wired up but disable it completely in the firmware settings and then rely on the GPS functionality of INAV 7.1 for all the autonomous flight modes.

Pawel released another video earlier today with a bit more information and some demonstrations which is linked to below. Be aware that flight modes such as position hold will only work for so long without a magnetometer before the quad then starts to drift or starts toilet bowling.