Thanks!Appears that the installed wireless mini-card is replaceable.
Reference link:
https://downloads.dell.com/manuals/all-products/esuprt_laptop/esuprt_inspiron_laptop/inspiron-15-3521_owner's manual_en-us.pdf
Removal/Replacement procedure starts on Page 37.
Do verify that I did find the correct Service Manual for your laptop.
And the following link seems to match:
https://www.ifixit.com/Guide/Dell+Inspiron+15-3521+Wireless+Card+Replacement/31938
I found an Intel wireless adapter that may work.
Newegg: Intel Dual Band Wireless-AC 8260 (8260.NGWMG)
Key is to verify that the replacement wireless adapter with 2.4 GHz and 5.0 GHz is supported by the laptop.
Read requirements and specs very carefully.