There are several identifiers of panoramas.

Your photos have (probably) been tagged automatically by the creating software. Hugin for example adds:

Projection : Equirectangular (2) FOV: 360 x 180 Ev: 14.64

to the images caption / description exif tags and

Hugin

to the Stitching Software tag.

The image sharing website flickr has a facility to display 360 panoramas and identifies them through metadata.

flickr Equirectangular group discussion

XMP-GPano-FullPanoHeightPixels=[enter_height]
XMP-GPano-FullPanoWidthPixels=[enter_width]
XMP-GPano-ProjectionType=equirectangular
XMP-GPano-UsePanoramaViewer=True

Those tags as explained here: https://exiv2.org/tags-xmp-GPano.html are googles photo sphere xmp tags so it's reasonable to assume an android phone has added these (see also https://developers.google.com/streetview/spherical-metadata).

Finally the format of 360x180 panoramas is a 2:1 pixel ratio.

All you need now is some software (or a script) that allows you to search for these things.

Edit:

As a linux user I thought I'd be able to go straight to a cataloguing tool such as digikam DAM, Digital asset management for Linux, but the best I can do is an advanced search for Aspect Ratio = 2:1. The problem is this will include any image cropped to 2:1 as well. Unless there is something else in the description to help, you will get a lot of false positives. Digikam imports image metadata into a library in the form of a SQlite3 database file which is queried by digikam for it's searches and forms. It might be possible for external software to produce a list of images based on the gpano tags. For the scripters and coders exiftool can search for metadata and return a list too.

This might be a two parter for someone else to finish...