This is normal and is usually caused by display differences, not a Lightroom export problem.

If you export in sRGB for web use, that is generally the correct choice. The bigger issue is that computer monitors and phone screens often show color differently. A computer display may be uncalibrated, too bright, or too cool, while many phones use vivid display modes that boost saturation. Even two calibrated screens can still look different because they have different brightness, gamut, and rendering.

What you can do:

• Keep exporting in sRGB for general web sharing.
• Calibrate/profile your computer monitor if you want more accurate editing.
• Check whether your phone has a Standard/Natural mode instead of Vivid.
• Edit with moderate saturation and realistic brightness.

What you cannot do:

• Force other people’s phones or screens to display your photos the same way.

So the short answer is: your export settings are probably fine; the mismatch is mainly due to differences in screen calibration, color gamut, and phone display processing.