Maybe you could downgrade it in the F-Droid store, but for me I haven’t had any issues with the version of microG that comes with the JP2061, even with MobilePay. You just have to manually install MobilePay version 10.16.0 (4429694), because later versions have issues with device registration/PIN acceptance.
If you don’t know how to install certain version manually, you go to the MobilePay’s store page in the Aurora Store, hit the three dots in the top right corner, select “Manual download” and then enter the number 4429694 to the promt.