[Sony Xperia XA2 Questions & Answers] DHD4Me:
I tested again with new results. There picture all made with the snap camera (org.lineageos.snap (2.02.072).

If could be that there is a problem with meta information in pictures. I delete all metainfo with

exiftool -all= IMG_20210517_164126_snapcam.jpg

and after this I can select the picture in signal for sending.

Next step I wanted post the image here and delete the gps info for anonym post. ;) I get a warning of exiftool with the info that is fixed.

exiftool -a -gps:all= IMG_20210517_164126_snapcam_metaorig_noGPS.jpg
Warning: [minor] Entries in IFD0 were out of sequence. Fixed. - IMG_20210517_164126_snapcam_metaorig_noGPS.jpg
Warning: [minor] Entries in ExifIFD were out of sequence. Fixed. - IMG_20210517_164126_snapcam_metaorig_noGPS.jpg
1 image files updated

After this the picture can also select in signal for sending.

It is possible that there is the problem?

Here are the complete meta info with "xx" in gps tags of the original picture which not work.

[ExifTool] ExifTool Version Number : 11.88
[System] File Name : IMG_20210517_164126_snapcam_metaorig.jpg
[System] Directory : .
[System] File Size : 4.6 MB
[System] File Modification Date/Time : 2021:05:17 16:41:26+02:00
[System] File Access Date/Time : 2021:05:17 17:00:09+02:00
[System] File Inode Change Date/Time : 2021:05:17 17:00:09+02:00
[System] File Permissions : rw-r--r--
[File] File Type : JPEG
[File] File Type Extension : jpg
[File] MIME Type : image/jpeg
[File] Exif Byte Order : Big-endian (Motorola, MM)
[File] Image Width : 4624
[File] Image Height : 2608
[File] Encoding Process : Baseline DCT, Huffman coding
[File] Bits Per Sample : 8
[File] Color Components : 3
[File] Y Cb Cr Sub Sampling : YCbCr4:2:0 (2 2)
[IFD0] Camera Model Name : QCAM-AA
[IFD0] Orientation : Horizontal (normal)
[IFD0] Modify Date : 2021:05:17 16:41:26
[IFD0] Y Cb Cr Positioning : Centered
[IFD0] Resolution Unit : inches
[IFD0] X Resolution : 72
[IFD0] Y Resolution : 72
[IFD0] Make : QCOM-AA
[ExifIFD] ISO : 40
[ExifIFD] Exposure Program : Not Defined
[ExifIFD] F Number : 2.0
[ExifIFD] Exposure Time : 1/106
[ExifIFD] Sensing Method : One-chip color area
[ExifIFD] Sub Sec Time Digitized : 269088
[ExifIFD] Sub Sec Time Original : 269088
[ExifIFD] Sub Sec Time : 269088
[ExifIFD] Focal Length : 4.2 mm
[ExifIFD] Flash : Off, Did not fire
[ExifIFD] Metering Mode : Average
[ExifIFD] Scene Capture Type : Standard
[ExifIFD] Focal Length In 35mm Format : 24 mm
[ExifIFD] Create Date : 2021:05:17 16:41:26
[ExifIFD] Exif Image Height : 2608
[ExifIFD] White Balance : Auto
[ExifIFD] Date/Time Original : 2021:05:17 16:41:26
[ExifIFD] Brightness Value : 3.6
[ExifIFD] Exif Image Width : 4624
[ExifIFD] Exposure Mode : Auto
[ExifIFD] Aperture Value : 2.0
[ExifIFD] Components Configuration : Y, Cb, Cr, -
[ExifIFD] Color Space : sRGB
[ExifIFD] Scene Type : Directly photographed
[ExifIFD] Shutter Speed Value : 1/106
[ExifIFD] Exif Version : 0220
[ExifIFD] Flashpix Version : 0100
[InteropIFD] Interoperability Index : R98 - DCF basic file (sRGB)
[InteropIFD] Interoperability Version : 0100
[GPS] GPS Img Direction Ref : Magnetic North
[GPS] GPS Latitude Ref : North
[GPS] GPS Img Direction : xx
[GPS] GPS Latitude : xx deg xx' xx.xx"
[GPS] GPS Longitude Ref : East
[GPS] GPS Longitude : xx deg xx' xx.xx"
[GPS] GPS Altitude Ref : Above Sea Level
[GPS] GPS Altitude : xxx m
[GPS] GPS Time Stamp : 14:41:20
[GPS] GPS Processing Method : ASCII
[GPS] GPS Date Stamp : 2021:05:17
[Composite] Aperture : 2.0
[Composite] Image Size : 4624x2608
[Composite] Megapixels : 12.1
[Composite] Scale Factor To 35 mm Equivalent: 5.7
[Composite] Shutter Speed : 1/106
[Composite] Create Date : 2021:05:17 16:41:26.269088
[Composite] Date/Time Original : 2021:05:17 16:41:26.269088
[Composite] Modify Date : 2021:05:17 16:41:26.269088
[Composite] GPS Altitude : xxx m Above Sea Level
[Composite] GPS Date/Time : 2021:05:17 14:41:20Z
[Composite] GPS Latitude : xx deg xx' xx.xx" N
[Composite] GPS Longitude : xx deg xx' xx.xx" E
[Composite] Circle Of Confusion : 0.005 mm
[Composite] Field Of View : 73.7 deg
[Composite] Focal Length : 4.2 mm (35 mm equivalent: 24.0 mm)
[Composite] GPS Position : xx deg xx' xx.xx" N, xx deg xx' xx.xx" E
[Composite] Hyperfocal Distance : 1.69 m
[Composite] Light Value : 10.0

If I take pictures with open camera then there is no problem.